[CentOS] Planning Mail Server (with low resources)

>>I agree. I would use openfiler and have two front end servers mounting the 
>>disk over NFS. This means you will have to run courier imap.
> 
> 
> No, it just means you need to use maildir format which qmail uses
> natively and the other transports can do via procmail.   Dovecot
> can use it on the imap side.
> 

or maildrop :P