Lots of emails being flagged as Virus infected

Hi

Our server is setting lots of emails as containing viruses.

We have tracked several and they have are emails sent from a scanner direct with the pdf attached so there does no seem to be any way they could become infected.

Is this normal, or can we do something about it.

Thanks for your time.
Greg

Operating system Debian Linux 4.0
Webmin version 1.430
Virtualmin version 3.61 (Pro)
Theme version 6.1
Time on server 03/Sep/2008 14:23
Kernel and CPU Linux 2.6.18-5-686 on i686

Operating system Debian Linux 4.0
Perl version 5.008008
Path to Perl /usr/bin/perl
Postfix version 2.3.8
Mail injection command /usr/lib/sendmail -t
BIND version 9.3.4
Apache version 2.2.3
PHP version 4.4.4, 5.2.0
Webalizer version 2.01-10
Logrotate version 3.7.1
MySQL version 5.0.32
ProFTPd version 1.30
SpamAssasssin version 3.1.7-deb
ClamAV version 0.90.1

Status: 
Closed (fixed)