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