If you want to access your mailbox across a network using mail user agents (MUAs) such as Eudora, Microsoft Exchange, Pegasus, mutt and fetchmail, you must run the qmail POP server. The qmail POP server allows these clients to read and delete mail from their mailbox, but doesn’t include a method for sending email; use qmail-smtpd or ofmipd for that.
Consistent with qmail’s component design, the qmail POP server is actually three separate programs that cooperate to create the POP service. (Traditional POP servers such as qpopper are typically implemented as a single large program.)
The qmail POP server only handles Maildirs, not mbox mailboxes or anything else. If you are installing qmail on an existing mail system, you must convert any existing mailboxes to Maildir if you want to use the qmail POP service. (If you want to keep using mboxes, you can use the popular qpopper POP server, which is not covered here.)
The qmail POP server consists of a set ...