Often times a service is functioning properly, but mail will not deliver. The general root cause for this is the mail service silently rejecting mail, or sometimes a firewall change.
All outgoing mail should be sent via the internal mail relay listed in Terraform outputs.
SMTP Authentication should be used to send mail. In order to communicate, the username and password need to be sent base64 encoded:
# Get the username in base64 echo -n "username" | base64 # Get the password in base64 echo -n "password" | base64
Sending a test email
“VXNlcm5hbWU6” is base64 for “Username:”. “UGFzc3dvcmQ6” is base64 for “Password:”.
# Connect to the server openssl s_client -starttls smtp -connect RELAYIP:25 AUTH LOGIN 334 VXNlcm5hbWU6 PASTE-YOUR-BASE64-USERNAME-HERE 334 UGFzc3dvcmQ6 PASTE-YOUR-BASE64-PASSWORD-HERE 235 2.7.0 Authentication successful MAIL from: <email@example.com> 250 2.1.0 Ok RCPT to: <firstname.lastname@example.org> 250 2.1.5 Ok DATA 354 End data with <CR><LF>.<CR><LF> From: email@example.com To: firstname.lastname@example.org Subject: Our mail really does work We have worked with the best scientists abroad, and found that indeed this works. . 250 2.0.0 Ok: queued as A0F8860435 QUIT 221 2.0.0 Bye