> I don't have a problem to solve, but I don't know which mail server to > use either. But, like I said, ideally I'd like to use one of the > groupware type mailserver (POP3, SMTP, IMAP, calendar, address book, etc) > What you want is a centralised and yet distributed user information database whether mysql, postgresql, ldap and centralised but yet distributed mail storage. Just about any MTA that can be installed on Centos will support the first be it qmail, sendmail, postfix or exim. IMAP/POP3 wise, dovecot or courier-imap can also support the first. The second is best to hide from the application layer by implementing it at the file system level with say GFS. Address book can be plain old ldap. Calendar...sorry that is even more integrating. You might want to try JES (Java Enterprise System) besides the others that you have mentioned. Thunderbird has calendar support. Oh, happy integrating and interface buliding/modifying for this lot. If you are looking for a server solution for outlook, please just go and either get Exchange or go trouble the guys running OX and so on because Centos has zero solutions that support Outlook with all its features in force.