[Dovecot] passwd-file and MySQL

[Paolo]

Speaking about multiple DB ...

A my customer has a server (CentOS 6.x, dovecot 2.0.x, postfix, 
Squirrel+RoundCube with vacation and password plug-in), with about 3.000 
users (about 200 different domains), all defined as system users and home 
as /home/mail/%user%

The system works fine. Its only additional interest is authenticating 
users like user at domain.tld / password (maintaining also the 
current user.domain / password).

Is it possible and How complex configuring a similar environment?

Only matter of sync /etc/shadow and DB or other problems?

Regards, Paolo