OK, encontrei o erro e resolvi sozinho ...
$ sudo vi /etc/login.conf
dovecot:\
:openfiles-cur=512:\
:openfiles-max=2048:\
:tc=daemon:
$ sudo cap_mkdb /etc/login.conf
$ sudo /etc/rc.d/dovecot stop
$ sudo /etc/rc.d/dovecot start
De / var / log / maillog
Nov 12 16:14:39 server dovecot: master: Dovecot v2.2.15 starting up for imap
Nov 12 16:14:53 server dovecot: imap-login: Login: user=<info>, method=PLAIN, rip=192.168.1.1, lip=192.168.1.30, mpid=18612, TLS, session=<oEWnZ1kk8wDAqAEB>
Obrigado ...