Sounds like you are probably smarter about Hylafax than I am but... just thought I would try to help.
When I did not have the faxmaster set up how I wanted it, I would see emails from Hylafax in /var/spool/mail. They were just in a file called "fax". Maybe your mails are going there.
Also, check in etc/aliases. Don't know your distro, but suse uses the list in there to decide where emails go, i.e. system emails. I think I had to add who the faxmaster is in that file.
Also, maybe unrelated, I have in /etc/hosts this note:
# hylafax seemed to suggest to put this in. 10 June 05
# because sendfax was saying: "Can not reach server at host "localhost", port 4559"
127.0.0.1 localhost loopback
Anyway, maybe not very helpful, but good luck.