Replicate IMAP folder hierarchy to your local drive
Kolab ist eine freie Groupware-Lösung. Sie besteht aus dem Kolab-Server und den dazugehörigen Schnittstellenimplementationen in einer ganzen Reihe verfügbarer Kolab-Clients.
OfflineIMAP is a tool to simplify your e-mail reading. With OfflineIMAP, you can read the same mailbox from multiple computers. You get a current copy of your messages on each computer, and changes you make one place will be visible on all other systems. For instance, you can delete a message on your home computer, and it will appear deleted on your work computer as well. OfflineIMAP is also useful if you want to use a mail reader that does not have IMAP support, has poor IMAP support, or does not provide disconnected operation.
I have found that this is the easiest combination that allows you to serve Virtual Domains, and Users. With this it's also very easy to implement webmail systems like SquirrelMail.