Sending via SMTP

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

Setting	Value
Host	`smtp.sendmux.ai`
Port	`587` with STARTTLS, or `2525` with STARTTLS
Username	Any value, such as `smtpuser`
Password	Your `smx_mbx_` send-only key, mailbox password, or owner-approved Sending-resource `smx_agent_` token
Authentication	`LOGIN` or `PLAIN`

Test with swaks

swaks --to user@example.com \
  --from hello@example.com \
  --server smtp.sendmux.ai:587 \
  --auth LOGIN \
  --auth-user smtpuser \
  --auth-password "smx_mbx_your_key_here" \
  --tls \
  --header "Subject: Test email" \
  --body "Hello from Sendmux"

SMTP vs HTTP

Need	Use
Existing SMTP-only tool	SMTP
New application integration	HTTP API
Batch sending	HTTP API
Built-in retry protection	HTTP API
Native MIME message handling	SMTP

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.

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.

Sending by HTTP

Sending accounts

Getting started

SDKs

CLI

Integrations

AI integrations

Teams and access

Sending

Receiving

Monitoring

Billing

Webhooks

Sending via SMTP

Connection details

Test with swaks

SMTP vs HTTP

What happens next

Send by HTTP

API keys

Delivery logs

​Connection details

​Test with swaks

​SMTP vs HTTP

​What happens next

​Related guides

Send by HTTP

API keys

Delivery logs

Connection details

Test with swaks

SMTP vs HTTP

What happens next

Related guides