custom checkpassword + imap server

[DNS Monster]

I wrote my own version of checkpassword, which works great
in combination with qmail-pop3d. I tried to figure out how
to plug it into Courier-imap 1.3.0 but cound not. The
question is, has anyone gotten custom checkpassword to work
with Courier or/and is there another IMAP server that speaks
Maildir and could use checkpassword for authentication?