I'm getting a little involved now, thanks for replaying guys
Disable Imap and only keep pop3 ?
but how can I grant students' mobility around labs, keeping their Inbox's messages available from one workstation to another?
The suggestions about memory is very useful. I'll put spanassassin and mailscanner but only after a hardware upgrade.
by now I consider: cyrus and postfix
The suggestions have been very important. I'll continue reading in this direction. Any last comments are also welcome :)
I'll keep the last partitioning, passed 8 hours I'll install, now need a rest :) zZZZ
I would like to keep this topic open, for any new suggestion on a different and new setup on Planning Mail Server (with low resources).
Thanks guys for all your help and time, this is a very nice and active place.