Have ISPConfig 3 running on fedora 21. Address mail.nevity.com Added config files. Squirrelmail working and can read/send messages as expected. Using imap is a different story tho - can not connect tunderbird to send/receive emails. Testing with telnet and openssl seem to give all correct responses. Can login, receive list. Some of the errors I managed to read from the journald when I try to connect thunderbird : Jul 24 15:35:52 xxxxxx postfix/smtpd: improper command pipelining after EHLO from xxxxxxxx: QUIT\r\n Jul 24 15:35:52 xxxxxx postfix/smtpd: disconnect from xxxxxxxx Is this related?