Often by default, postfix is configured to deliver email messages in mbox format. To convert mbox to Maildir
Edit /etc/postfix/main.cf and look for a line
"Maildir/" for qmail-style delivery (the / is required).
home_mailbox = Maildir/2. if procmail is used by postfix to deliver locally change /etc/procmailrc add a line
DEFAULT=$HOME/Maildir/3. restart postfix4. for new users to have Maildir/ after creation domkdir -p /etc/skel/Maildir/new
mkdir -p /etc/skel/Maildir/cur
mkdir -p /etc/skel/Maildir/tmp5. convert all existing users to Maildir format using an effect perl script from qmail.org download it at http://www.qmail.org/convert-and-createwget -c http://www.qmail.org/convert-and-createthen run it sh convert-and-createNote: for dovecot no need to change anything, it will autodetect mail box formats, very cool.