[Mimedefang] Mimedefang not calling spamassassin

[Steve Pfister]

Sorry if this is something obvious, but I'm kind of stuck. I'm using RedHat
Linux 9,  sendmail 8.12.11, mimedefang 2.39,  and spamassassin 2.63. MD
seems to be running fine, and does seem to be invoking the virus scanner
(clamav 0.65), but never calls spamassassin. My mimedefang-filter is based
on the example minimum filter for windows clients, with very little
modifications (if any). If I do a mimedefang.pl -features, it shows:

SpamAssassin                  : yes
Mail::SpamAssassin            : Version 2.63

It looks like it should be called, but nothing ever happens. What might I be
missing?

Thanks!