Simple Mail Transfer Protocol (SMTP)

SMTP is an Internet standard communication protocol for electronic mail transmission

Troubleshooting

TLS

1. Prepare encoded strings for your mail username and password:

   echo -ne "mail@example.net" | base64

2. Connect to mail server:

   openssl s_client -starttls smtp -connect smtp.example.com:587

3. Send Extended Hello:

   EHLO

4. Authenticate:

   AUTH LOGIN
   <your-encoded-username>
   <your-encoded-password>

If that's successful the mail server should return 235 2.7.0 Authentication successful