First install Postfix, and Dovecot, and remove sendmail:
yum install postfix yum install dovecot yum remove sendmail
Next configure postfix (/etc/postfix/main.cf) to deliver mail to Maildir directories instead of the default mbox. I'm also assuming you already know how to configure Postfix to accept mail for the domain youo want it be authoritative for.
home_mailbox = Maildir/Send a message to a local user and check the maillog to make sure it was delivered correctly. Messages to that user should be stored in:
/home/(user)/Maildir/newAssuming mail is getting delivered to that user's mailbox simply start Dovecot and login with that username/password. Dovecot only listens on IMAPs by default, edit the /etc/dovecot.conf to enable any other protocols you want to run (IMAP, POP3, or POP3s). Dovecot will use a generic SSL cert with localhost.localdomain as the server name. You can make your own cert using the following command:
openssl req -new -x509 -nodes -out /tmp/public.pem -keyout /tmp/private.pem -days 3650 cp /tmp/public.pem /usr/share/ssl/certs/dovecot.pem cp /tmp/private.pem /usr/share/ssl/private/dovecot.pem service dovecot restart
Done! Grand total of about 10 minutes of tweaking to get a fully workable SMTP/IMAP/Maildir solution.
Note: I even configured Postfix to have procmail process and deliver the mail which gives even more flexibility. Just remember to have your .procmailrc deliver to Maildir directories (directories ending in a /) as the default is mbox.