imap authentication - shadow vs mysql

[Konra Wawryn]

Hi,

I`m looking for some opinions about authentication process for the 
systems with more than 1000 E-mail accounts.
Maybe some one could advise me what is the best authentication method.

At the moment I`m storing all passwords in my /etc/passwd. My IMAP 
server is growing and I`m planning to build new host, my question is: 
what is the best authentication model for IMAP server ? Do I need to 
store all user/passwords in mysql or maybe in LDAP ?

I`m searching for some solution which will help me to scale my system in 
the future.


Maybe some one could advice me ?


Greetings

Konrad