Log to be checked if using roundcube
tail -fn0 /var/cpanel/roundcube/log/errors
That's the error - "[04-Jun-2011 02:51:01 +0400]: IMAP Error: Login failed for contact @ koh.ro from 18.104.22.168. AUTHENTICATE PLAIN: Authentication failed. in /usr/local/cpanel/base/3rdparty/roundcube/program/include/rcube_imap.php on line 192 (GET /cpsess7117936613/3rdparty/roundcube/index.php)"
Please go to WHM > Change Hostname and ensure to re-save the new hostname. After doing that, move these files:
mv userdomains userdomains.bak110603
mv trueuserdomains trueuserdomains.bak110603
mv domainusers domainusers.bak110603
After moving those files, then run this command:
You will get messages about the files you've moved no longer existing. Those files will be recreated by the command.