SMTP
Send through any SMTP server or relay.
Provider type: SMTP server
Host: smtp.example.com
Port: 587
Encryption: STARTTLS
Username: you@example.com
Password: ••••••••Any server that accepts SMTP works: Amazon SES SMTP, Mailgun, Brevo, your own Postfix, an internal relay.
Add the provider
- Open Providers → Add Provider, Provider Type: SMTP server.
- Fill in the fields:
| Field | Value |
|---|---|
| Host | The server's hostname. |
| Port | Usually 587 with STARTTLS, or 465 with SSL/TLS. |
| Encryption | STARTTLS (default): the connection is upgraded, and Senlo refuses to continue if the server does not offer it. SSL/TLS: encrypted from the first byte. None: unencrypted. |
| Username, Password | Leave both empty for a relay that accepts mail without authentication. |
- Click Create Provider, then select it in your workspace's Settings.
Match Encryption to the port. None sends the message and the password in the clear; use it only inside a private network.
Sending
Senlo keeps a small pool of connections (up to 5) per SMTP configuration and reuses them, so large sends do not open a connection per email.
The From email on your triggers must be allowed by the server; most providers require a verified domain.
No delivery webhooks
SMTP has no standard way to report deliveries, bounces or complaints back. With an SMTP provider the delivery log shows SENT or FAILED, but not DELIVERED, BOUNCE or SPAM_REPORT, and bounced addresses are not suppressed automatically. Senlo's own open and click tracking still works.
If your provider has its own webhooks (SES, Mailgun), Senlo does not read them yet. Use Resend or Postmark for automatic bounce handling.
Cloud only
On senlo.io the SMTP host must be on the public internet: hosts like localhost, *.internal, *.local and private IP ranges are refused.