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Use SMTP when an existing application, plugin, or mail client already supports SMTP delivery.
The SMTP password is your smx_mbx_ send-only key or mailbox password. 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.

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Connection details

SettingValue
Hostsmtp.sendmux.ai
Port587 with STARTTLS, or 465 with implicit TLS
UsernameAny value, such as smtpuser
PasswordYour smx_mbx_ send-only key or mailbox password
AuthenticationLOGIN or PLAIN

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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"

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SMTP vs HTTP

NeedUse
Existing SMTP-only toolSMTP
New application integrationHTTP API
Batch sendingHTTP API
Built-in retry protectionHTTP API
Native MIME message handlingSMTP

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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.