I followed this tutorial. The only difference is that I used a 2nd level domain e.g.: something.example.com instead of example.com. I tested Postfix following the instructions at page 4, and I have created a user with phpmyadmin and sent him a welcome email with mailx. Everything seems to be fine, but when I try to login via squirrelmail I get the following error (unknown user or password incorrect) : tail -50 mail.info and tail -50 mail.log show that indeed the login failed: Code: Nov 5 14:59:25 mail imapd: LOGIN FAILED, user=test, ip=[::ffff:127.0.0.1] Nov 5 14:59:30 mail imapd: LOGOUT, ip=[::ffff:127.0.0.1], rcvd=39, sent=332 Nov 5 14:59:39 mail imapd: Connection, ip=[::ffff:127.0.0.1] Nov 5 14:59:39 mail imapd: LOGIN FAILED, user=test, ip=[::ffff:127.0.0.1] Nov 5 14:59:44 mail imapd: LOGOUT, ip=[::ffff:127.0.0.1], rcvd=39, sent=332 Nov 5 15:00:11 mail imapd: Connection, ip=[::ffff:127.0.0.1] Nov 5 15:00:11 mail imapd: LOGIN FAILED, user=test, ip=[::ffff:127.0.0.1] Nov 5 15:00:16 mail imapd: LOGOUT, ip=[::ffff:127.0.0.1], rcvd=39, sent=332 but they don't explain why that happened. Any ideas? Edit: I found what I was doing wrong. I had to login with username "[email protected]" instead of just "test".