Problem with relaying relayed mail

GW6.0-SP4

From a fax-solution an incoming fax is packed as
pdf-attachement into a mail to a specific user. Since this
user has the same function as "info@" the mail gets relayed
by rule to a real user. This real user checks the fax and
depending on the content relays it as attachement to someone
else. The process is clear so far and works fine.

Now when relaying this mail with pdf-attachement this e-mail
is not attached itself, but some other old mail from the
real users mailbox. This only happens when relaying those
fax-mails. When relaying normal mails addressed to "info@"
(which also are relayed to the real user) there are no
problems at all.

Hopefully someone here can tell where to start.

Sincerely

Karl