[otrs] FAQ: Using PostMaster.pl with fetchmail

Instead of using pop3, I would like to use imap-ssl to retrieve trouble ticket emails to be handled by otrs. According to the documentation, the best way to do that is to use fetchmail and then parse it to PostMaster.pl? How to do that? I tried to do something like (test .fetchmailrc in /tmp)

fetchmail -a -f /tmp/.fetchmailrc | /path/to/PostMaster.pl

but what I got was the /var/spool/mail/otrs mailbox (which is where fetchmail is told to save the emails it gets. BTW, the fetchmail side of the business seems to work fine) was read in as if it was one single long email (as opposite to each email be read as a separate email). What am I doing wrong?