Product updates

Bug fixes

Outgoing usage now counts every accepted To, CC, and BCC recipient occurrence. If the same address appears more than once, each accepted occurrence is billed; addresses rejected before acceptance are not charged.Delivery log summaries show accepted and rejected recipient totals. Log details list each recipient outcome in sending order.Blind-copy addresses remain part of delivery without being exposed in the delivered message headers.Repeated account setup requests reuse work already in progress. When a newer setup email is issued, its link replaces the earlier link so only the latest setup link can be used.

Bug fixes

If automatic disabling cannot finish, the sending account stays available for retry. Sendmux preserves its recent failure history. The next failure retries the status change instead of incorrectly treating the account as disabled.

Bug fixes

When a provider connection is temporarily rate-limited, Sendmux now returns a clear retry response instead of a server error.The total, active, and error counts above sending accounts are now clickable, so you can filter the list in one step.

Bug fixes

Successful deliveries now reliably clear earlier provider failures. If that reset is temporarily unavailable, Sendmux retries it without sending the email again, preventing stale failures from disabling a healthy provider.

Bug fixes

Emails accepted by your configured provider are no longer sent again when delivery logging or usage tracking is temporarily unavailable. This prevents duplicate delivery and charges after acceptance.

Bug fixes

Verified domains no longer remain active when their required bounce-handling records or upstream provider setup later stop matching.Scheduled verification confirms the failure twice before marking the domain failed, so a temporary lookup problem does not change an active domain’s status.Required bounce-handling setup now repairs automatically after a mismatch, with retries if the repair is interrupted.Scheduled verification now continues through every eligible domain, so large domain inventories no longer leave later domains unchecked.

Bug fixes

Domain verification now accepts valid combined SPF records and stronger DMARC policies, so tightening your DNS settings no longer marks a healthy domain as failed.Temporary DNS or provider lookup errors now leave the domain unchanged. Domains marked failed by the earlier check can return to active automatically after a complete successful verification.Domain-failure alerts now continue working when a domain’s normal sending setup is unavailable, and queue acceptance is no longer reported as a sent message.

Bug fixes

Billing now waits until you continue to payment before loading the payment form. If it cannot load, you can retry without restarting checkout.Payment failures now show a clear, safe message instead of technical details.

Bug fixes

Emails sent from an active shared mailbox using team credentials now use that mailbox’s sending route instead of being incorrectly rejected.Credit checks now also match the shared mailbox route before an email is accepted.

Improvements

New accounts now verify the email address before password or passkey setup, while existing addresses receive the same neutral on-screen response.

New featuresImprovementsBug fixes

Sending account transfers

You can now export supported non-secret sending account settings as a versioned JSON configuration file, then import it to update matched accounts. Passwords and connected-account credentials are never included or accepted in this format.

Improvements

New and reset passwords now require at least 15 characters and are checked against known-compromised choices. Existing shorter passwords continue to work for sign-in.Password sign-in now uses the same failure behaviour for unknown accounts and incorrect passwords, reducing account disclosure.Large sending account imports now upload more reliably before processing starts.Inbox attachments now upload as soon as you select them. Draft saving and sending wait for every file to finish.

Bug fixes

CSV exports for sending accounts and delivery logs now write formula-like values as text, so spreadsheets do not treat exported data as formulas.Oversized Management and Mailbox API JSON requests now return 413 payload_too_large before being processed.

ImprovementsBug fixes

Account access

Passkey sign-in now starts with your email address, improving account privacy while keeping existing passkeys compatible.Google and GitHub sign-in now avoid linking an existing Sendmux account based only on a matching email address. Returning social sign-ins continue to use their already linked provider identity.Password recovery now invalidates older reset links and signs out existing sessions after a password change, so recovered accounts do not leave prior access active.

Bug fixes

AI tool workflows can now upload and download mailbox attachments through hosted MCP without hitting an unintended permission block.Short-lived Sending API upload links now reject invalid tokens or mismatched upload headers before reading file bytes, keeping delegated uploads safer and more predictable.

Bug fixes

Inbox thread lists now load more reliably for conversations with attachments, reducing timeouts without changing attachment details when you open a message.If a message is deleted while the list is loading, Sendmux now omits the incomplete thread instead of showing blank details.

Bug fixes

Connected Gmail and Microsoft 365 sending accounts that need attention now offer a direct Re-authorise action, so you can reconnect without deleting and recreating the account. The Last used value now updates after sending and shows the recent activity time.

Bug fixes

Team invitations now stay pending even when email delivery needs attention, so you can resend a fresh invitation later.Bulk invites and resend actions now show a clear warning when an invitation was created but delivery needs attention, instead of treating the whole invite as failed.

ImprovementsBug fixes

Teams

Team invites and membership changes now respect team capacity at every step, including resending or reactivating pending invites.Creating many teams in quick succession now has clearer safeguards, so accidental repeats and automated abuse are blocked before setup starts.

Inboxes

Inbox labels now have a sensible per-team limit, while restoring an existing label still works.

Bug fixesImprovements

Sending API

Binary attachment uploads now require the exact Content-Length header in the OpenAPI spec, Postman collection, SDKs, CLI, and MCP guidance. Sendmux file helpers calculate it from local files, so agents can upload attachments without placing file bytes in prompts.

Improvements

Sending API

Agents can now upload Sending API attachment bytes first and send by attachment_id, keeping normal files out of prompts and JSON base64 payloads.Hosted agents can mint a short-lived upload URL, upload with the returned headers and no Sendmux API key in the upload command, then attach the returned attachment_id to single or batch sends.

Mailbox API

Mailbox attachment download links are now shorter and use stable attachment refs, making them easier to pass through agent tools and command-line workflows.Existing short-lived download links keep the same expiry and safety model, while fresh message and attachment reads return the new compact link shape.

Developer tools

MCP clients can now read text attachments directly through mailbox_read_attachment, so agents no longer need a separate web fetch step for common files like Markdown recipes.Hosted MCP Sending tools now support direct attachment uploads and delegated upload URLs, so agents do not need to handle API keys or base64 payloads.

Improvements

Domain verification

Custom domains now show the extra bounce-handling DNS records needed for Amazon SES MAIL FROM, including the bounce. subdomain MX and TXT records.Domain verification now checks those bounce records separately and keeps already verified domains active while the extra DNS records are pending.The Management API now returns MAIL FROM status and DNS check results for domains, and zone file exports include the same records so teams can copy the full DNS set at once.

New featuresImprovements

Mailbox API

Mailbox attachments can now be uploaded through short-lived presigned upload URLs. First authenticate to mint the URL, then upload the file bytes with the exact returned headers and no API key in the upload command.Mailbox direct uploads and presigned uploads share the same 7,500,000 byte per-attachment cap, and oversize uploads are rejected before a presigned URL is minted.Conditional message reads now refresh short-lived attachment download links instead of returning 304 Not Modified when the cached message metadata needs a new link.

Developer tools

The CLI can now attach local files directly on supported send commands, so file bytes stay out of prompts and shell-generated base64 strings.SDK file helpers now attach local files without manual base64 encoding, and MCP attachment tools now guide agents toward local file paths or presigned uploads before falling back to tiny inline base64 content.When inline attachment content is too large, agent-facing errors now point to lower-token file path, presigned upload, CLI, and SDK helper options.

Bug fixes

Transactional emails now use more reliable light backgrounds and stronger text contrast across inboxes, including verification, password reset, invite, billing, domain, and webhook alerts.Email buttons, footer text, and supporting details now use safer colour pairs, so messages stay readable in preview panes and clients that adjust display colours.

New featuresImprovements

Mailbox API

Mailbox attachment metadata now includes short-lived download_url values that can be fetched without an Authorization header. Re-read the message or attachment metadata to renew the URL after it expires.Mailbox message lists, message reads, thread reads, search results that include attachments, and live mailbox events now return complete attachment metadata for agent workflows.

Developer tools

MCP now includes tools to fetch fresh attachment metadata, upload attachments before sending, and wait briefly for new mail without manual polling.The SDKs and CLI have been regenerated from the updated Mailbox API, and the CLI can now follow mailbox events with mailbox:stream-events --follow.

Bug fixes

SMTP sending now validates envelope addresses before choosing a delivery path, preventing a MAIL FROM required rejection for messages that should use your configured providers.If a message can only use Amazon SES and the sender domain is not configured in Sendmux, the rejection now explains that the domain must be configured for Amazon SES delivery.

New features

Account access

You can now sign in or create an account with GitHub, alongside the existing email, passkey, and Google options.Existing accounts can be linked by verified primary email, and your security settings now identify GitHub sign-in sessions.

Bug fixes

Delivery and incoming log date filters now include the full selected end date, so choosing a date includes activity throughout that day instead of stopping at midnight.Log pages, CSV exports, and API log lists now apply the same date filters, keeping result counts aligned across refreshes and exports.

New featuresImprovementsBug fixes

Management API

You can now check whether a mailbox address is available before you create it, including shared @myagent.mx addresses and custom-domain addresses.Availability checks now explain why an address cannot be used, including invalid addresses, unavailable domains, existing mailboxes, reserved addresses, and cleanup that is still in progress.

Mailboxes

Shared @myagent.mx mailbox setup now relies on the verified shared domain identity with Amazon SES, instead of creating separate sender identities for each mailbox address.Deleting a mailbox now keeps its address unavailable until cleanup finishes, so recreating the same address no longer races with deletion.

Bug fixes

Mailbox setup and deletion retries now recover more reliably after partial failures, so repeated attempts can continue from the last confirmed state instead of duplicating work.

ImprovementsBug fixes

Onboarding

New users now go straight from email verification into full-screen first-team setup. Solo setup is shorter, and team setup covers invites, mailbox setup, and sending choices in a single flow.Existing users now get a lighter full-screen setup for new teams, without the dashboard sidebar getting in the way.

Email verification

The verification screen is more concise, with direct Gmail and Outlook links plus a reminder to check junk mail.

Bug fixes

First-team invites now handle duplicate addresses and partial send failures more reliably. Team and mailbox creation can still finish if one invite needs attention.

ImprovementsBug fixes

Inboxes

Archiving or deleting a selected email now opens the next email automatically, so you can keep moving through your inbox without an extra click.When you open a newly created mailbox from the confirmation window, Sendmux now takes you straight to that mailbox’s inbox.

Onboarding

The setup panel now moves to the next step after you choose a sending, receiving, or combined setup path.Setup steps now match the path you chose. Sending setup points you to the details needed to send mail, receiving setup points you to mailbox creation and inbox checks, and combined setup walks through both receive and reply testing.

Visual refresh

Sendmux now uses an updated blue accent across light and dark mode for a more consistent brand feel.

Bug fixes

Agent approval requests now appear in the notifications panel for team owners.Opening the notifications panel now closes the account menu.Valid promo codes can now be used again on later top-ups when the code allows repeat use.

New featuresImprovementsBug fixes

Notifications

The app now includes a Notifications panel in the account menu, with unread counts, read controls, and a new Notifications settings tab for choosing email and in-app updates by category.Agent sending approvals now appear as actionable notifications, so owners can review pending approvals from the notifications panel.The Notifications panel now uses a cleaner header, making updates easier to scan.

Agent access

The agent access guide now tells agents to save the full credential bundle in a secure store immediately after registration, so later MCP, CLI, SDK, mailbox, and sending workflows can continue without re-registering.Approving or revoking agent sending access is now more reliable, including for teams where mailbox setup finishes after the owner has already joined.Owners can now review all agent access requests from a fuller team panel, filter by status, search requests, and approve or decline selected agents in bulk.

Teams

Team settings now live on the team page, including delete-team controls at the bottom. Team names can also be edited directly from the page title.

Bug fixes

Agent-created @myagent.mx mailboxes can now send once the owner approves sending, without asking the owner to add a custom domain first.Mailbox sending setup now recovers from partial setup states more reliably, so retries can finish without duplicate sending providers.Shared mailbox setup retries now treat already-complete sending setup steps as successful, preventing false failure alerts during automated recovery.Mailbox sending setup recovery now treats already-existing delivery event notifications as complete, so retries can finish instead of stopping on duplicate setup state.

Bug fixesImprovements

Agent access

Agent owner invite links now handle already accepted invitations cleanly for the invited owner. If you are already a member of the invited team, the link takes you to the team instead of showing an invitation error.Agent-created teams now receive the normal initial credit once the invited human owner joins the team.Pending agent sending approvals are now surfaced in the account menu, so owners can spot an agent that is waiting for sending access without first opening the members page.The agent access recipe now keeps the owner-invite step directly after token setup and includes a copy-paste proof-of-work example, so agents can complete registration from auth.md without stopping after a receive-only token.When token exchange needs mailbox setup to finish, the response now includes retry timing in both the body and header so agents can back off cleanly.

New featuresImprovements

Agent access

Owners can now approve sending for an invited agent after joining the team. Until then, pre-claim agent tokens stay receive-only.The team page now includes an Agent access card where permitted team members can approve or revoke an agent’s sending capability.Agents can exchange their claim token after owner approval to get a send-capable smx_agent_ token for the Sending API, without the owner creating or copying a separate API key.Anonymous agent registration now starts with a short-lived proof-of-work challenge before a temporary mailbox is provisioned. Agent-auth rate-limit responses also include retry guidance so legitimate agents can back off cleanly.

Docs

The agent access, API key, SDK, CLI, MCP, Sending API, and Agent Skills docs now describe which token types work for each surface, how owner approval fits into auth.md adoption, and how agents should handle registration challenges.The public auth.md examples, agent access guide, and agent-auth metadata now use the canonical identity_endpoint field and Sendmux-prefixed extensions without older compatibility aliases.

ImprovementsBug fixes

Agent access

Agents that call the Management API without credentials now receive the standard authentication discovery hint, so they can find the protected resource metadata and complete setup from a bare API request.The agent access guide now includes request and response examples for registration, token exchange, owner invites, credential use, revocation, expiry, and errors, so agents can follow the signup flow without guessing field names.Discovery metadata also now advertises the supported bearer-token method alongside the agent access endpoints.The same discovery hint is available from both the base Management API path and the mailbox entry point.Agents that already have credentials continue to receive the normal API response from those entry points.

Bug fixes

Unclaimed agent registrations are now cleaned up after their 24-hour expiry, including pre-claim tokens, pending owner invites, and the temporary agent mailbox.Invalid agent invite requests can no longer spend the owner email safety limit before the agent credential is checked. Expired temporary agent mailbox names can also be reused after cleanup.

Bug fixes

Mailbox lists now keep active mailboxes visible even when a team has many recently deleted mailboxes, so Mailboxes and Inboxes show the same active mailbox set.

New features

Agent access

Agents can now discover Sendmux through auth.md, create an agent-managed team with one free @myagent.mx mailbox, and invite a verified human owner.Pre-claim agent tokens can read mailbox data and receive mail, but they cannot send mail until a human claims the team.

Improvements

Hosted MCP

Agents can now discover Sendmux’s OAuth protected resource metadata from the app domain, including the supported authorisation server and scopes, so connection setup can start from standard OAuth discovery.

New features

Developer tools

Sendmux SDKs are now available for TypeScript, Python, Go, PHP, and Ruby, with package-managed installs from npm, PyPI, the Go module proxy, Packagist, and RubyGems.The sendmux CLI is now available from npm, with profile management and JSON output across generated Management, Mailbox, and Sending commands.MCP is now available through hosted OAuth, with local stdio and self-hosted HTTP options when you run the server yourself. You can grant Management, Mailbox, Sending, or any combination, and agents only see the tools allowed by that grant.

Bug fixes

Reply, reply all, and forward shortcuts now use the latest message in the open thread when no individual message is selected, so replies from sent conversations keep the right recipients.
Inbox refreshes now ignore late message updates after you switch folders, searches, or selected messages, so the reader stays aligned with your current view.

Improvements

Management API

Pending shared Amazon SES limit increase requests can now be cancelled through the Management API. Once cancelled, the team can submit a new request when they are ready.

New featuresImprovements

Domains

Custom domains can now be set up for sending only, or for sending and receiving. Sending-only domains require ownership, SPF, DKIM, and DMARC records, and leave incoming mail with your current provider.

Improvements

Domains that send and receive still include mailbox setup and MX records.
Sending-only domains can be switched to sending and receiving later.
The Management API now documents the domain mode field and the upgrade endpoint.

Bug fixes

New mailbox keys now confirm access before they are shown, so you can use the returned key immediately.
If key setup is temporarily unavailable, the Management API now returns a retryable service unavailable response instead of showing a key that is not ready yet.

Bug fixes

Inboxes

Inboxes now reset the compose window whenever you reply, reply all, or forward from a thread, so recipients and subjects match the message you selected even if a compose window was already open.

Bug fixes

Reply and reply all now pre-fill the correct recipient from the selected message.
Inbox actions such as archiving or deleting now refresh the thread list after you navigate away and return, so changed messages do not reappear from cached page data.
Thread lists now stay aligned with the current mailbox, folder, and search even when a refresh finishes after you have switched views.
Starting another compose action now saves the current draft before replacing the compose window, including when the draft is minimised.
Inboxes with many messages now load thread lists more reliably by fetching attachment details only when a message is opened.
Message opens, draft autosaves, sends, and label actions now refresh only the current inbox data needed, so those actions feel faster in day-to-day use.

ImprovementsBug fixes

Credentials

Team credential limits now count manual API keys and connected apps together. Quota labels across the app now use credentials, so usage matches what counts toward the limit.

Bug fixes

Creating a new connected app is now blocked when the team has reached its credential limit.
Re-authorising the same connected app still works at the limit because it replaces the existing connection instead of adding another credential.

ImprovementsBug fixes

Connected apps

Connected app authorisation now groups permissions by area and lets you choose none, read, full, or a custom set for each group. This makes broad Management API grants easier to scan before you connect an agent.

Bug fixes

Connected app authorisation now grants only the permissions selected in the consent flow.
Re-authorising mailbox access now always uses the selected mailbox set instead of falling back to a single-mailbox grant shape.

Bug fixesImprovements

Mailbox sender rules

Sender allow/block rules on the mailbox detail page now save and persist reliably. Previously a rule could appear saved in the editor but be missing after a page refresh.

Improvements

Wildcard patterns like *@example.com are now accepted and saved as the bare domain (example.com), which allows or blocks the entire sender domain at delivery.
When a rule can’t be saved, the editor shows a persistent inline error explaining why, instead of only a brief notification.
The sender filters API now accepts the documented note field on rules, and rejects rule sets whose rule type contradicts the selected mode instead of silently dropping them.

Bug fixes
Fixed saved sender rules not appearing on the mailbox page after a refresh.

Bug fixes

Hosted MCP

All-product-line MCP connections no longer ask for a mailbox when an agent uses Management API or Sending API tools. Mailbox selection is still required only for Mailbox API tools when more than one mailbox is granted.

Improvements

Hosted MCP

Hosted MCP can now grant one or more selected mailboxes in the same connected app. Agents can search the granted mailbox set, target a mailbox for each mailbox action, and remain blocked from any mailbox that was not authorised.

Mailbox API

Connected app Mailbox API requests now support per-request mailbox_id targeting. Use GET /mailbox/mailboxes to list or search the mailboxes available to the token before making a request for a specific mailbox.

Bug fixes

Re-authorising the same MCP connected app now replaces earlier active grants for that app, so API keys shows a single current connection instead of stale duplicate connected-app rows.

New featuresImprovements

MCP

Hosted MCP authorisation now lets you choose the Management API, Mailbox API, Sending API, or any combination in one connected app. Agents only see the tools for the product lines you grant, and unavailable tools remain blocked by the credential permissions.Local MCP setups can now use the same product-line selection for one, several, or all product lines.Local all-product-line MCP setups can use separate keys for each product line, so teams can keep least-privilege key boundaries while still giving an agent the full curated toolset.Hosted MCP Sending tools now keep the same permission, sending-scope, and rate-limit checks as direct Sending API calls before each send request is accepted.

Credentials

Connected apps now appear separately from manual API keys. They use short-lived access tokens with refresh tokens, can be filtered in API keys, and disconnecting an app revokes its connected-app access without creating orphan manual keys.Re-authorising an existing connected app now replaces its previous product-line grant, so removed product lines disappear from that app instead of leaving stale access behind.

SDKs and CLI

SDK and CLI surfaces now account for every documented operation and expose the supported options and filters.

ImprovementsBug fixes

Hosted MCP

Hosted MCP authorisation now lets you choose the right team before granting access. Available resources refresh when you switch teams, so connected apps only see what that team can use.

Improvements

Connected app requests now use clearer team wording throughout the authorisation flow.
Authorisation checks now validate current team access again before creating connected app credentials.

Bug fixes

Hosted MCP requests now avoid a network path that could fail for otherwise valid agent actions.
Malformed authorisation requests with duplicate fields are now rejected more consistently.

Bug fixes

Inbox quota sync now tells clients when quota data should be refetched instead of returning an invalid sync error.

Bug fixes

Newly-created inbox keys now confirm access before they are shown, so they work immediately for the inbox API, IMAP, SMTP, and JMAP.
Inbox folder deletion now retries brief setup delays after a folder is created or renamed, reducing transient delete failures.
Inbox deletion now retries temporary cleanup delays more reliably.

Bug fixes

Inbox folder and message update/delete requests now honour If-Match when you send it and avoid hidden stale-state checks when you make sequential changes without conditional headers.
Deleted inboxes and domains now clean up associated routing and filtering state more consistently.

New features

Hosted MCP

Teams can now connect supported agent tools to Sendmux through a hosted MCP endpoint, authorise access in the browser, and grant only the inbox and account permissions they choose.

Improvements

The authorisation flow now has clear sign-in, consent, success, denied, and error states.
Headless clients can use scoped access tokens with the same permission checks as browser-based connections.
Agent tools now follow the same Sendmux role and key permissions used by the API, so unavailable actions stay hidden and blocked.

ImprovementsBug fixes

Inboxes

Inbox credentials now use provider-issued secrets while preserving Sendmux key IDs, improving compatibility with the managed mailbox platform.

Improvements

Rotating an inbox credential now tracks the provider credential ID directly, so stale credentials can be cleaned up more reliably.
Mailbox roles now use the current managed-mailbox permission model for sending, receiving, and inbox access.

Bug fixes

Inbox provisioning now recovers more safely if external credential creation succeeds but the local operation has to retry.

Bug fixes

Creating a mailbox on the shared Sendmux domain now checks the shared-domain setup before provisioning the mailbox, so generated addresses no longer fail when required domain records are missing.
Domain creation and deletion now consistently protect the shared Sendmux domain while still letting teams delete the mailboxes they created.
Sign-up legal links now use shorter labels so the agreement line fits better on narrow screens.

Bug fixes

Sign-up, email verification, and checkout tracking now handles redirects more reliably.
Sensitive URL parameters are now removed from tracked page and referrer metadata.
A growth reporting view now loads grouped activation and revenue metrics without failing on aggregate sorting.

ImprovementsBug fixes

Dashboard

The team overview now points sending activity to the sending logs, keeps capacity cards as read-only usage summaries, and raises separate deliverability issues when bounce and complaint rates are both above recommended levels.

Inboxes

Compose now handles send and draft saving more cleanly, so sent messages close out instead of continuing to save as drafts.

Improvements

Delivery log statuses now show short readable labels instead of raw provider event strings.
Dashboard hover details now avoid repeating the same health summary in more than one place.
Billing runway and usage-capacity cards now use clearer labels and more predictable interactions.

Bug fixes

Draft autosave now backs off while a message is sending, reducing duplicate saves and avoidable rate-limit warnings.
Email buttons now render with a consistent background across email clients.
Deliverability alerts now count bounce rate and complaint rate separately when both need attention.

ImprovementsBug fixes

Dashboard

The team overview health strip now uses clearer status colours, relative timing, and concise hover details so quiet teams do not look broken.

Improvements

Status blocks now use filled healthy, warning, and issue states in light and dark mode.
Health details now stay concise on hover, with exact timestamps available where timing matters.

Bug fixes

Quiet inbound periods no longer count as active issues when there is no mail to receive.
Activity date labels now stay stable instead of shifting by timezone.

ImprovementsBug fixes

Dashboard

The team overview now presents health, sending, receiving, billing, domain, API key, and capacity signals with clearer states for new, partially configured, and active teams.

Improvements

The health strip now fills completed hours and shows the selected hour’s sent, received, and failed counts directly in the summary.
Activity chart tooltips now match the dashboard style and stay compact while you inspect daily sending and receiving totals.
Domain status now uses the latest saved verification details so SPF, DKIM, and DMARC signals can be shown independently after checks run.

Bug fixes

Empty or low-activity teams no longer show misleading healthy indicators, fake billing runway, or internal dashboard wording.
Duplicate API key names no longer trigger repeated-row rendering warnings in the overview.

Improvements

The sending API and supporting test packages now use updated dependency versions that resolve current npm security advisories without changing the public API.

New featuresImprovementsBug fixes

Dashboard

The team overview now shows a clearer health summary with recent sending, receiving, webhook, billing, domain, API key, and capacity signals together in one place.Activity charts now use cached rollups so dashboard refreshes stay fast for busy teams.

Improvements

The API reference now uses cleaner operation names and shared response models, improving generated SDK method names and response types.
The Inboxes sidebar item now shows an unread count when new mail is waiting.
The dashboard sidebar now separates feedback from account top-up controls more clearly.

Bug fixes

Email threads in Inboxes now keep message bodies readable in dark mode, including replies with their own text colours.

ImprovementsBug fixes

Improvements

New teams now start on the managed Amazon SES sending route with a 50-email daily limit before requesting a review.
Inboxes now let you move conversations into another folder from the context menu when that folder accepts mail.
The Inboxes compose window now turns completed recipients into tidy address chips after you move out of the field, while leaving unfinished input untouched.
The Compose button now sits above the inbox folder list for faster access.
Sending and receiving log tables now show relative times with the full date and time available on hover.

Bug fixes

Long inbox threads now scroll inside the message reader instead of making the whole app page taller.
Closing a compose window with draft content now saves the pending draft before closing, while Discard still skips saving.

ImprovementsBug fixes

Improvements

The dashboard sidebar now narrows on smaller screens and keeps Documentation, Feedback, balance, and Top up inside the scrollable menu.
The Inboxes page now gives more room to the open message on narrower desktop screens while keeping the folder menu and conversation list usable.

Bug fixes

Sending and receiving log tables now fit typical browser widths without unnecessary horizontal scrolling.
Long message IDs in log tables now show a short readable prefix, so columns stay aligned while the full value remains available.
Drafts now autosave once the basic message details are present, and the Drafts count updates after the first save.
Inbox folder counts now only appear where they are meaningful: unread Inbox, all Drafts, and all Spam.
Mailbox filters now hide inactive or deleted mailbox addresses.
Incoming log senders now show the message sender instead of a message identifier.
The Compose keyboard hint is now easier to read.

New featuresImprovementsBug fixes

Incoming logs

Teams can now open Logs under Receiving to review inbound messages that count toward usage. Each entry shows the mailbox, sender, recipients, subject, event type, received time, and amount, with search, filters, and pagination for larger histories.The Management API now includes GET /inboxes/logs and GET /inboxes/logs/{public_id} so you can audit the same incoming log data programmatically.

Dashboard

The overview dashboard now shows incoming email totals, standard received mail, spam received mail, and incoming usage alongside sending stats.

Improvements

Webhook event selection now includes search, making it faster to choose the right events when setting up or editing a webhook.
The dashboard setup checklist now adapts better on small screens and keeps long task lists within the viewport.

Bug fixes

Inbox message bodies now use the selected light or dark theme, so rendered email content no longer appears with mismatched colours.
Draft conversations now open in edit mode from the Drafts folder, and edited drafts replace the previous draft when saved or sent.
Sent-folder conversations now sort by sent time and show the message from the selected folder instead of mixing in unrelated thread messages.
Inbox actions such as archive, delete, spam, and not spam now apply to the messages in the current folder, avoiding unexpected moves for the rest of the conversation.

New featuresImprovementsBug fixes

Inboxes

Teams can now open a shared Inboxes view from the dashboard. You can see mail across all team mailbox addresses, focus on one mailbox, search conversations, and filter by folder, read state, starred messages, attachments, or label.Threaded conversations now open in a reader with reply, reply all, forward, attachments, keyboard hints, message actions, and right-click shortcuts.

Labels

You can create, rename, recolour, delete, assign, and remove inbox labels from the dashboard. Labelled conversations now show a subtle coloured edge so they are easier to scan without crowding the message list.

Improvements

Mail actions now show progress with a subtle fade and status toast, so the inbox stays readable while an action completes.
The dashboard sidebar now has separate icons for Inboxes and Mailboxes.
The sidebar credit balance now stays usable in both expanded and collapsed modes.
Thread replies now refresh into the open conversation after sending.
Inboxes now refresh quietly in the background while the tab is visible, so new mail and folder counts stay current without interrupting your work.
The compose window now supports Command + Enter to send, with the shortcut shown on the send button.
Mailbox switchers now include search, so teams with many mailbox addresses can switch faster.
New teams now get an in-dashboard setup checklist that helps choose a sending, receiving, or combined workflow and tracks the key setup steps.
Mailbox quota bars now show live storage usage on the mailbox list instead of always showing zero usage.

Bug fixes

Folder-specific actions now hide when they do not apply, such as spam actions for drafts.
Archive, spam, and delete actions now resolve the available mailbox folders before moving messages.
Attachment downloads now preserve the original file bytes and metadata.
Slow inbox actions now time out cleanly instead of leaving the page stuck in a processing state.
Reply sends now move out of drafts correctly after queuing.
Delete actions now create or use a Trash folder so deleted conversations remain accessible from the inbox folder list.
Label changes no longer alter the mailbox colour marker shown beside each conversation.
Inbox send confirmations now use the same action-toast styling as other message actions.
Opening an unread conversation now clears its unread styling and folder count immediately, then refreshes quietly in the background.

ImprovementsBug fixes

Team setup

Team creation now uses a wider centred layout, so choices, preferences, and use-case details have more room while staying aligned with the rest of the dashboard.

Dashboard help

You can now open product documentation and send feedback from your dashboard sidebar.Feedback includes the page and team context needed to investigate requests, so you can report an issue, suggest an idea, or share praise without leaving the app.

Mailboxes

Mailbox creation now handles delayed sender-name setup without discarding the mailbox. If the sender display name cannot be applied immediately, the mailbox is still created and you can save the name again from the mailbox page.Deleted mailbox addresses can now be recreated cleanly. The new mailbox gets its own credentials and settings instead of inheriting state from the deleted mailbox.

Bug fixes

The consultation calendar loading state now separates the spinner from the loading text.
The final Open dashboard action now opens the new team’s dashboard overview.
The use-case field label now has the same spacing as other setup fields.
The dashboard feedback form now opens with the intended wider layout, app typography, and reliable submission handling.
Creating the first mailbox password now recovers cleanly if part of the operation is interrupted.
Mailbox setup now waits for new mailbox accounts to be ready before applying sender details and creating the first password.
If mailbox password setup needs extra time, the generated password is still shown once instead of creating a credential you cannot see.
Recreating a deleted mailbox address now rebuilds sender rules reliably, so the new mailbox is created instead of showing a retry error.
Rotating or revoking a mailbox password now avoids leaving the mailbox without a working credential if part of the change needs to retry.
Mailbox password changes now count in-progress credentials toward the team API key limit, so limits stay consistent while a change is being processed.
Deleting and recreating the same mailbox address now works without old mailbox state blocking the new mailbox.

New featuresImprovementsBug fixes

Team setup

Team creation now walks you through the setup details we need upfront: your team name, website, industry, how you found Sendmux, preferences, and what you’re building. If you want help, you can book a 15-minute consultation without leaving setup.Signed-in browser agents can create teams after login too, using retry-safe requests so automated onboarding doesn’t double-create a team when a request is retried.

Sending account management API

You can now manage sending accounts through the Management API: list accounts, add custom SMTP accounts, update account settings, activate or deactivate accounts, test custom SMTP connections, read usage, and request higher sending-account limits.The shared Amazon SES sending route can now be read, activated or deactivated, and sent for a daily-limit review from the API. Its platform-managed credentials, quotas, routing settings, and sender defaults stay protected.See Sending accounts.

Mailbox suspension

Mailbox suspension now consistently pauses inbound mail, outbound sends from that mailbox address, mailbox API access, SMTP access, and IMAP access until the mailbox is resumed.You can also suspend or resume a mailbox through the Management API with retry-safe requests.See Mailboxes and API keys.

Mailbox API attachments

Mailbox API session discovery now reports the final 25 MB outbound message limit alongside the per-attachment upload limit.Attachments uploaded through the Mailbox API are capped at 7.5 MB. Final outbound messages, including bodies, headers, and encoded attachments, must fit within 25 MB.See Mailbox API.

Improvements

The Sending API docs now link directly to the account-management endpoints that control which accounts can send.
The Management API reference now has a dedicated Sending accounts group.

Bug fixes

Mailbox credentials now stop working while their mailbox is suspended and work again after resume.
Sending from a suspended mailbox address is now blocked even when you use a broader sending credential.
Oversized uploaded attachments are now rejected before they can be used in a send request.
Oversized outbound messages are now rejected before partial send work starts, so clients get a clear payload_too_large response instead of a later send failure.

New featuresImprovementsBug fixes

Inbound email billing

Accepted inbound mail is now billed at $0.15 / 1,000 emails, matching standard outgoing usage. Mail rejected by mailbox sender rules is not billed.See Billing and Mailboxes.

Realtime mailbox events

The Mailbox API now includes GET /mailbox/events, a Server-Sent Events stream for message.received and message.received.spam. Use it for agents, CLIs, and SDKs that need live mailbox updates without polling.The stream supports heartbeats, bounded connection lifetimes, and resume with Last-Event-ID or last_event_id. If the replay window is no longer available, the stream tells the client to sync before reconnecting.See the Mailbox API event stream.

Team limits

Teams now have clear usage limits for domains, mailboxes, sending accounts, webhooks, and active API keys. When your team reaches 80% of a limit, you can request an increase from the relevant dashboard page and receive an email when the request is reviewed.

Improvements

Limit usage now appears at the bottom-right of the relevant dashboard pages, so it stays available without crowding the page header.
The API key limit now covers active root and mailbox-class credentials, including send-only and mailbox credentials.
The team limits guide now clarifies default limits, increase requests, and that email volume is not capped beyond existing sending limits.
Webhooks and mailbox realtime events use the same public message.received event names for inbound mailbox activity.

Bug fixes

Mailbox credential creation and rotation now respect the API key limit consistently.

ImprovementsBug fixes

Dashboard

The dashboard is clearer for larger teams and longer mailbox or webhook names.

Improvements

Mailbox lists now show Name before Email, with clearer column labels.
Long domain, mailbox, and webhook headings now stay on one line with cleaner truncation.
Long webhook endpoint URLs are clipped in lists and can be inspected from the hover tooltip.
Team menus now include a direct Invite members action.

Bug fixes

Invited team members are now taken into the invited team after accepting or signing up from an invitation, instead of being sent to create a new team.
Pending team invitations now appear in invitation history.
Pending team invitation banners now clear immediately after accepting or declining, without requiring a hard refresh.
Users with pending team invitations can now view and accept them without creating a separate team first.
Webhook 24h metric cards and charts now count recent deliveries consistently with the delivery log.
Sidebar account initials now come from the signed-in user’s name or email.

New featuresImprovements

Webhooks

Webhook subscriptions can now target all team mailboxes or a selected mailbox list, so you can route inbound events to the right service without creating a separate team.Use webhooks for server-to-server event delivery. Use the Mailbox API event stream when a mailbox client keeps a live connection open and needs immediate received-message updates.

Improvements

Webhook delivery logs now show attempts, retry timing, response status, latency, response previews, and retained request payloads from the last 7 days.
Failed-webhook emails now link directly to the delivery logs for the affected subscription.
Public event names now use product-shaped message.* names, including message.received and message.received.spam.

New featuresImprovements

Mailbox API

The Mailbox API now supports filtered message query changes, so clients can poll a saved message list and receive only added, removed, and reordered message IDs.

Improvements

Session discovery now reports supported Mailbox API capabilities, current state tokens, request limits, and intentionally unavailable features.
Message responses now expose active keywords, and batch message updates can set or clear custom keywords for richer mailbox triage.
Batch message deletes can move up to 100 messages to Trash, or permanently delete them when requested.
Mailbox credentials now have tighter permissions so restricted mailbox capabilities stay unavailable outside the public API. They remain usable for SMTP and IMAP access.

New featuresImprovements

Mailbox API for agents

The Mailbox API now gives agents more precise mailbox access without fetching full messages by default. You can retrieve raw bodies, clean JSON message content, clean thread content, exact message batches, counts, search snippets, thread metadata, folder change feeds, sender identities, send submissions, quota details, and compact usage health.See the Mailbox API.

Improvements

Message searches support richer filters and snippet-only responses so clients can decide what to fetch next.
Sync now covers messages, folders, threads, submissions, identities, and quotas through typed change polling.
Message and folder writes now have stronger stale-state protection, with If-Match support on supported deletes as well as updates.
Attachment sends can now use a binary upload step before messages/send, and attachment downloads support byte-range requests.
Attachment contents remain download-only; clean content endpoints return attachment metadata without parsing files.

New featuresImprovementsBug fixes

Managed Amazon SES sending route

Every team now gets a managed Amazon SES sending route out of the box — ready to send immediately, with no setup. It’s capped at 50 emails per day to protect your sending reputation. When you reach 80% of the cap you can request an increase in one click from the Accounts page; we review each request and email you the outcome.

New mailbox API

A new mailbox API lets you list folders and messages, read a message, send mail, and poll for changes — authenticated with a mailbox key. See the Mailbox API.

Improvements

One credential per mailbox. Each mailbox now uses a single credential for sending and for mailbox access over SMTP, IMAP, and the API — simpler setup. “App passwords” are now called “Mailbox passwords”.
Refreshed, more compact Accounts, domain, mailbox, and webhook pages, with DNS records and connection settings you can copy in a single click.

Bug fixes

The mailbox quickstart example now works exactly as shown.

ImprovementsBug fixes

Management API

The Management API is hardened for production use:

Consistent success and error response formats.
A request ID on every response for support correlation.
Cursor pagination on all list endpoints.
ETags and conditional requests (If-None-Match / If-Match) to save bandwidth and prevent lost updates.
Idempotency keys so create requests can be retried safely.
Rate-limit responses now report the exact number of seconds until your limit resets.

Bug fixes

Fixed a rare timing issue that could cause a small number of valid emails to be incorrectly rejected; affected messages now send normally.

New featuresBug fixes

Mailboxes

Create and manage mailboxes with per-mailbox storage limits, sender-filter rules, and suspend, resume, and empty actions. A shared domain option lets you start instantly with no setup.

Your own sending domains

Add your own sending domains with guided DNS setup (MX, SPF, DKIM, DMARC), one-click verification, automatic periodic re-verification, and a downloadable DNS zone file. See Domain management. Owners are emailed if a domain stops verifying.

Configurable webhooks

Subscribe to delivery and inbound-mail events with signed webhooks: name them, choose event types, send a test event, and rotate the signing secret. You’re notified if an endpoint starts failing. See Webhooks.

Deliverability

A new Deliverability page tracks your bounce and complaint rates over rolling windows and shows your sending reputation at a glance.

Bug fixes

Delivery, bounce, and complaint events are now recorded reliably to your event history.
Delivery-log statuses stay accurate even when provider events arrive out of order — a failed or bounced email is no longer shown as sent.

New features

Team deletion

Team Owners can now delete a team. Deletion has a 7-day grace period during which it can be undone; after that the team and its data are permanently removed.

Invitation management

Track full invitation history with filters, invite several people at once, resend or cancel pending invites, and decline an invitation.

New featuresImprovements

Team roles

Teams now have four roles — Owner, Admin, Developer, and Member — with permissions enforced across the dashboard and the API.

Low-balance email alerts

Get an email when your team balance drops below a threshold you choose, with a one-click link to top up.

Improvements

Refreshed, on-brand transactional emails — responsive, dark-mode friendly, and personalised with your name.
The overview now tracks pending emails alongside sent, successful, and failed, and large numbers are shown compactly (for example 1.5k, 2M).
The dashboard and logs refresh automatically while you’re viewing them and pause when the tab is in the background.

New features

Sendmux is here

Welcome to Sendmux. The initial release includes:

Dashboard — an at-a-glance overview with sending charts and a searchable, filterable delivery-log viewer with CSV export.
Sending accounts — connect accounts over SMTP or with Gmail and Microsoft 365 (including GCC High, DoD, and China clouds), organise them into groups, bulk-test connections, and import in bulk from CSV. See Sending accounts.
Sending API — send a single email or batches of up to 100 over a modern JSON REST interface, with structured sender and recipient objects, partial-success batch results, attachments, CC/BCC, and Reply-To. See the Sending API.
Read-only Management API — query your sending accounts, email logs, metrics, and billing programmatically, with API-key authentication and a published OpenAPI spec.
Scoped API keys — restrict a sending key to specific accounts or a group, and see warnings before deleting anything a key depends on.
Dollar-based billing — a clear transaction history, automatic top-ups so your balance never runs dry, and promotion codes at checkout.
Unlimited teams — create and join as many teams as you need.

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​Sending account transfers

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​Teams

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​Mailbox API

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​Email verification

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​Docs

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​Agent access

​Hosted MCP

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​Domains

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​Credentials

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​Connected apps

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​Mailbox sender rules

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​Hosted MCP

​Hosted MCP

​Mailbox API

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​MCP

​Credentials

​SDKs and CLI

​Hosted MCP

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Bug fixes

Bug fixes

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Bug fixes

Bug fixes

Bug fixes

Bug fixes

Bug fixes

Bug fixes

Improvements

Sending account transfers

Improvements

Bug fixes

Account access

Bug fixes

Bug fixes

Bug fixes

Bug fixes

Teams

Inboxes

Sending API

Sending API

Mailbox API

Developer tools

Domain verification

Mailbox API

Developer tools

Bug fixes

Mailbox API

Developer tools

Bug fixes

Account access

Bug fixes

Management API

Mailboxes

Bug fixes

Onboarding

Email verification

Bug fixes

Inboxes

Onboarding

Visual refresh

Bug fixes

Notifications

Agent access

Teams

Bug fixes

Agent access

Agent access

Docs

Agent access

Bug fixes

Bug fixes

Agent access

Hosted MCP

Developer tools

Bug fixes

Management API

Domains

Improvements

Bug fixes

Inboxes

Bug fixes

Credentials

Bug fixes

Connected apps

Bug fixes

Mailbox sender rules

Improvements

Bug fixes

Hosted MCP

Hosted MCP

Mailbox API

Bug fixes

MCP

Credentials

SDKs and CLI

Hosted MCP

Improvements

Bug fixes