Troubleshooting
SMTP not sending: what to check first
Most outbound email issues are authentication, port blocks, or policy problems. Start with these checks.
- Confirm SMTP authentication: username/password must be correct and SMTP auth must be enabled.
- Try an alternate port: if port 25 is blocked, use 587 or 2525 (or other offered ports).
- Check encryption: STARTTLS vs SSL/TLS must match what the server expects.
- Verify sender address: some relays require the sender or domain to be authorized.
- Look at error text: authentication failures, timeouts, and policy blocks usually say exactly what failed.