Legacy billing changed on 30 September 2026 at 05:00 UTC. Unpaid legacy teams
now use Free limits; extra Free teams are read-only until upgraded. Existing
resources, balances and paid access remain. Paid legacy teams keep top-ups and
use current rates, without an automatic Pro subscription.
Plans
With Free, you get two mailboxes and can send to up to 50 provider-accepted recipients per UTC day across all sending routes. These limits are fixed. If you hit one, delete an unused resource or upgrade to Pro. Provider quotas, safety controls, account health restrictions, and managed Amazon SES limits still apply on Pro.
Messages sent by a Free team add the plain text “Email sent via Sendmux” after supported text and HTML bodies. A blank gap separates it from your message. The footer has no link or Sendmux styling. Pro and Enterprise messages do not add it.
Every account can have one active Free team.
Keep your Free team and choose Pro for another.
A Pro team activates after confirmed checkout.
Paid legacy teams can keep their current billing setup or choose Upgrade to Pro on Billing. Pro activates after confirmed checkout at $7 per team each month plus usage.
Billing contact
Checkout asks for the team’s billing contact email. It can differ from your sign-in email, such as a shared accounts address. Sendmux uses this email for receipts and billing messages. Team membership, not the billing contact, controls ownership and access.Current usage rates
These rates apply to Free, Pro and preserved paid legacy teams. Enterprise rates follow the team’s contract. Sendmux charges each billable event individually. The per-1,000 column is only an equivalent rate for comparison; you do not buy or consume email in blocks of 1,000.
For outgoing mail, each provider-accepted To, CC, or BCC recipient occurrence is billed. Addresses rejected before provider acceptance are not charged.
If the same address appears in more than one recipient field, each provider-accepted occurrence is billed separately.
If a provider’s result is unknown, Sendmux keeps the reservation on hold while it reconciles the send. After 24 hours, unresolved holds are due for review; they are not automatically released. The hold is not a usage charge and cannot start an auto top-up by itself.
Inbound usage is counted for each distinct mailbox that receives the message. One message delivered to two mailboxes counts as two deliveries. Mail rejected by mailbox allow or block rules is not billed.
Storage is measured from mailbox usage and prorated by calendar day. One decimal GB is 1,000,000,000 bytes.
Usage transactions can be grouped, so the transaction table may show one Incoming email usage line for several received messages in a short period.
Balance
The Billing page shows current balance, purchased amount over the last 30 days, and consumed amount over the last 30 days. When a new team is set up, it receives $1 in credit. Current usage charges consume that balance even on Free. Once depleted, a Free team cannot buy more credit and must upgrade to Pro. Other eligible teams can top up before retrying a request that failed for insufficient credit.Manual top-up
Manual top-up is available to Pro, Enterprise and preserved paid legacy teams. Choose how much you want to add and complete checkout. The supported amounts are:Auto top-up
On Free, you can’t use auto top-up. For eligible teams, it adds balance when the team’s balance drops below a threshold. Add a default payment method before enabling automatic top-ups.
Use a monthly limit that covers expected usage but still caps unexpected spend.
Low-balance alerts
Low-balance alerts email you when team balance drops below the selected threshold.Transactions
The transaction table shows balance movements with type, amount, date, and description. Use it to reconcile purchases, auto top-ups, usage, refunds, and manual adjustments.API access
Use the Management API to read balance, summary, and transaction history from your own reporting tools.Management API
Open the generated Billing endpoint reference.
Related guides
Send by HTTP
Handle billing errors on sending requests.
Team limits
Review Free hard limits and Pro capacity.
Mailboxes
Use sender rules to reject unwanted inbound mail before it is billed.
API keys
Create keys for billing reporting.