Skip to main content
Use SMTP when an existing application, plugin, or mail client already supports SMTP delivery.
The SMTP password is your smx_mbx_ send-only key, mailbox password, or owner-approved Sending-resource smx_agent_ token. Routing still follows that key or mailbox scope.
Managed Amazon SES is for transactional email only. Use your own provider for marketing, newsletters, or bulk promotional sends.

​
Connection details

​
Test with swaks

​
SMTP vs HTTP

​
What happens next

Successful SMTP sends appear in Logs like HTTP sends. Use the message ID, sender, recipient, status, provider, and timestamp to trace delivery.

​
Free daily limit

Free teams can send to 50 accepted recipients per UTC day across SMTP and HTTP. Sendmux reserves capacity before returning 250, so concurrent SMTP sessions cannot cross the cap. When no daily capacity remains, SMTP returns 550 5.7.1 Daily sending limit reached. Upgrade to Pro to continue. The message is not queued. Retry after 00:00 UTC or upgrade the team to Pro.

Send by HTTP

Use the API for new integrations and batch sends.

API keys

Create the credentials used as SMTP passwords.

Delivery logs

Search and export SMTP delivery results.