Bcc addresses

Some of my users get mail inwhich (apparently) they have been blind
copied.  I use fetchpop1.9 to get our mail off a remote server and
then pass the mail to procmail to be delivered.  The problem is that
the Bcc addresses are gone and the mail winds up with the postmaster
and I have to guess who the mail belongs to so that it can be properly
forwarded.  Is there any way to solve this problem using procmail or
is it a sendmail question?

Dorita