How do you test relay authentication?

Testing relay authentication verifies your credentials work before relying on them for production sending.

Using swaks (recommended):

swaks --to test@example.com --from you@yourdomain.com --server smtp.relay.com:587 --auth --auth-user your_username --auth-password your_password --tls

• Shows full authentication exchange
• Reports success or exact failure reason
• Using openssl + manual commands:
• openssl s_client -starttls smtp -connect smtp.relay.com:587
• Then manually type:
• EHLO yourdomain.com
• AUTH LOGIN
• [base64 encoded username]
• [base64 encoded password]
• Server responds with success or error
• Using an email client:
• Configure Thunderbird, Outlook, or similar with the relay settings
• Send a test message
• Check for authentication errors in client or server logs
• What to verify:
• Correct hostname and port
• TLS/SSL works properly
• Username format (sometimes email, sometimes account ID)
• Password is correct
• Account has sending permission
• Common authentication issues:
• Wrong port (587 for submission with STARTTLS, 465 for SMTPS)
• Credentials need URL encoding for special characters
• Account requires 2FA/app-specific password
• IP restrictions blocking your test location