MailScanner fails to insert headers

[hermit921]

I have a few cases lately where messages go through our MailScanner 4.23
setup (with postfix).  I can see their entries in maillog.  They don't get
either the virus header or spam header that messages normally get.  The
messages I have in hand are very short, with only an email address in the
body -- assuming the users managed to forward the entire email.  Any ideas
why this would happen?

hermit921