Hi,
after the automatic installation of MU 13, all users are unable to login through horde. In the smtpd_debuglog I see:
Aug 29 09:36:03 plesk courier-imapd: Connection, ip=[::ffff:127.0.0.1]
Aug 29 09:36:03 plesk courier-authdaemon: received auth request, service=imap, authtype=login
Aug 29...