I have a slightly weird setup, using symlinks in ~/Maildir:

  $ ls -l /home/edward/Maildir | grep INBOX | sort
  drwx------ 5 edward edward    4096 2009-12-05 15:32 INBOX
  drwxr-xr-x 5 edward edward    4096 2009-12-05 15:29 INBOX.old
  lrwxrwxrwx 1 edward edward       9 2009-12-05 15:45 cur -> INBOX/cur
  lrwxrwxrwx 1 edward edward       9 2009-12-05 15:45 new -> INBOX/new
  lrwxrwxrwx 1 edward edward       9 2009-12-05 15:45 tmp -> INBOX/tmp

I configured sup to source mail from the directory "/home/edward/Maildir".

"sup-sync --changed" found new emails, but sup's polling mode didn't.

I've now started afresh, pointing sup at "/home/edward/Maildir/INBOX", and
everything's working fine -- both sup-sync and sup itself are seeing new mails
added to that Maildir.

Ed