Originally Posted by fobicodam
I tried to use maildir once but i couldnt retrieve the emails with pop3, does it need a how to or something?
If you want to use maildir, you will have to do 2 steps:
1) Install a maildir capable pop3 and IMAP daemon like courier.
2) Switch to maildir in ISPConfig under management > server > settings on the mail tab.
But be aware that all emails that have not been fetched by your customers from their mbox files will be inaccessible after the change.