> ## Documentation Index
> Fetch the complete documentation index at: https://sendmux.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Domains

> Add, verify, and manage custom domains for sending and receiving.

Use a custom domain when you want branded sending, hosted mailboxes, or both. Choose the domain mode when you add it: sending only avoids MX changes, while sending & receiving lets you create mailboxes after verification.

## Domain options

| Option                             | Best for                                           | DNS required   |
| ---------------------------------- | -------------------------------------------------- | -------------- |
| `myagent.mx` shared domain         | Fast tests and simple agents                       | No             |
| Custom domain, sending only        | Branded outbound mail while another inbox receives | TXT and CNAME  |
| Custom domain, sending & receiving | Branded mailboxes hosted in Sendmux                | TXT, CNAME, MX |

<Note>
  Each team starts with **25 domains**. See [Team limits](/docs/guides/team-limits).
</Note>

## Add a domain

<Steps>
  <Step title="Open Domains">
    Open **Domains** in the team workspace and select **Add domain**.
  </Step>

  <Step title="Enter the domain">
    Enter the domain you own, such as `mail.example.com` or `example.com`.
  </Step>

  <Step title="Choose usage">
    Choose **Sending only** if Sendmux should only send from the domain. Choose
    **Sending & receiving** if Sendmux should also receive mail and host
    mailboxes on the domain.
  </Step>

  <Step title="Copy DNS records">
    Sendmux shows the records required for your chosen usage. Sending-only
    domains do not show or check an MX record.
  </Step>

  <Step title="Publish the records">
    Add each record at your DNS provider. Copy values exactly as shown.
  </Step>

  <Step title="Verify">
    Select **Verify** after the records have propagated. Sending-only domains
    check ownership, sending policy, message policy, email signing, and bounce
    handling. Sending & receiving domains also check inbound routing.
  </Step>
</Steps>

## DNS records

| Purpose         | Record     | Required for        | What it does                                   |
| --------------- | ---------- | ------------------- | ---------------------------------------------- |
| Ownership       | TXT        | Both modes          | Confirms you control the domain.               |
| Email signing   | CNAME      | Both modes          | Enables DKIM signing through Amazon SES.       |
| Sending policy  | TXT        | Both modes          | Authorises Sendmux to send for the domain.     |
| Message policy  | TXT        | Both modes          | Defines DMARC handling for suspicious mail.    |
| Bounce handling | MX and TXT | Both modes          | Routes bounce handling through a subdomain.    |
| Receive mail    | MX         | Sending & receiving | Routes inbound mail for the domain to Sendmux. |

You can download the records as a zone file from the domain detail page.

## Enable receiving later

Open the sending-only domain and choose **Switch to sending & receiving**. Sendmux adds the MX requirement, resets the domain to pending, and asks you to verify again. Add the MX record before creating mailboxes.

## Verification states

| State      | Meaning                                                          |
| ---------- | ---------------------------------------------------------------- |
| `pending`  | Records are missing, still propagating, or still being checked.  |
| `verified` | All required records are present and ready.                      |
| `failed`   | One or more records could not be verified after repeated checks. |

Sendmux rechecks domains every six hours. A short DNS issue does not immediately trigger an email. Persistent failures notify team owners.

## Troubleshooting

<AccordionGroup>
  <Accordion title="Ownership is not found">
    Check that the TXT record name and value match Sendmux exactly. Some DNS
    providers append the zone name automatically, which can duplicate the
    domain.
  </Accordion>

  <Accordion title="Inbound routing is not found">
    This only applies to sending & receiving domains. Check that the MX record
    is on the same domain you added to Sendmux. DNS proxying features do not
    apply to MX records.
  </Accordion>

  <Accordion title="SPF is failing">
    Keep only one SPF record for the same domain name. Merge all `include:`
    values into the same TXT record.
  </Accordion>

  <Accordion title="Bounce handling is failing">
    Check the MX and TXT records on the `bounce.{your-domain}` subdomain. The MX
    record must use the target Sendmux shows, and the TXT record must match the
    generated SPF value.
  </Accordion>

  <Accordion title="DMARC is failing">
    Check that the TXT record is published at `_dmarc.{your - domain}` and still
    includes the policy value Sendmux generated.
  </Accordion>

  <Accordion title="Email signing is still pending">
    DKIM records can take longer to verify. Confirm all three CNAME records are
    present, then wait and verify again.
  </Accordion>
</AccordionGroup>

## Delete a domain

Deleting a sending-only domain stops sending from it. Deleting a sending & receiving domain is blocked while active mailboxes still use it. Delete or move those mailboxes first, then delete the domain.

After deletion, remove the DNS records from your DNS provider if you no longer need them.

## API access

Use the Management API when you want to create, list, upgrade, verify, or delete domains from your own tooling. Keep API shape, permissions, and error handling in the generated reference so your client follows the current contract.

<Card title="Management API" icon="book-open" href="/docs/api/introduction">
  Open the generated Domains endpoint reference.
</Card>

## Related guides

<Columns cols={2}>
  <Card title="Mailboxes" icon="inbox" href="/docs/guides/mailboxes">
    Create addresses on verified sending & receiving domains.
  </Card>

  <Card title="Domain settings" icon="settings" href="/docs/guides/domain-settings">
    Review inbound controls for sending & receiving domains.
  </Card>

  <Card title="Sending accounts" icon="mail" href="/docs/guides/sending-accounts">
    Connect providers for outbound sending.
  </Card>

  <Card title="Team limits" icon="gauge" href="/docs/guides/team-limits">
    Request more domain capacity.
  </Card>
</Columns>