I just finished following this tutorial on Digital Ocean for configuring a Dovecot, MySQL, and Postfix email server. I did not follow it to the end. (I didn't install Spam Assassin.) I also used a self-generated SSL temporarily. Other than that, I followed the tutorial to the letter. At every point where I was told to do a test command, I did so and the results were what the author said they should be.
The problem is that using an email client (like Thunderbird) I cannot login to the server. However, using Telnet I can connect to SMTP on ports 587 and 25. I can also connect to IMAP on port 993. (25, 587, and 993 are the ONLY ports I have forwarded from my external IP.)
I have checked the data in the MySQL DB. My user exists with my desired password.
How can I troubleshoot the issue here? Is there a way to test login credentials using telnet?
EDIT
Authentication is the issue. I've initiated the connection with openssl s_client -connect mail.example.com:587 -starttls smtp (Thanks 84104). My exchange then looks like this…
ehlo example.com
250-hostname.example.com
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-AUTH PLAIN LOGIN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
AUTH LOGIN
334 VXNlcm5hbWU6
MyBase64EncodedUsername
334 UGFzc3dvcmQ6
MyBase64EncodedPassword
535 5.7.8 Error: authentication failed: Connection lost to authentication server
Is there a debugging route I can take to find the problem? Is this simply authentication or a connection issue?
Best Answer
smtpd_tls_auth_only = yesmeans that telnet isn't going to be a viable option for credential testing. You really don't want to do the TLS negotiation by hand.Instead use something like
openssl s_client, e.g.openssl s_client -connect mail.example.com:587 -starttls smtp.Once connected you can then issue the standard commands. The exchange should look similar too: