Clam AV + POSTFIX + SpamAssanin

Aleksandar Milivojevic amilivojevic at
Tue Mar 1 14:45:54 UTC 2005

Michael Leung wrote:
> Hi all,
>    Pervious, I have installed POSTFix + SpamAssassin. They are doing
> the job very well. They can stop the spammer sending Virus and spam.
> But there is still a leak in email server. If one of our user got the
> email contains virus from a person he/she knows, not spammer,
> SpamAssassin may not stop this. So I have installed Clam AV. Does any
> one try to config it with POSTFIX + SpamAssanin? Would it be very
> slow? The message has to pass spamd and clamd.

I'm using MIMEDefang with Sendmail.  MIMEDefang controlls ClamAV and 
SpamAssassin, and does bunch of other sanity checks on emails (dropping 
malformed attachments, blocking prohibited file extensions such as exe 
and so on).

What I found is that ClamAV is usually very fast and lightweight.  Much 
faster than SpamAssassin.  If you are using both of them, your 
bottleneck will be SpamAssassin.  The only case when ClamAV is using 
lots of resources (memory and CPU) is when scanning huge archive files 
(such as ZIP).  You might opt to limit maximum size of email that 
Postfix will accept, or not to scan emails larger than certain size 
(viruses are highly unlikely to hide in huge emails).  Or simply be 
prepared that some smartass will bring your machine down when he 
attempts to send pictures from his compact flash card in single email 
(half gig card will suffice, provided it was full) ;-)

Aleksandar Milivojevic <amilivojevic at>    Pollard Banknote Limited
Systems Administrator                           1499 Buffalo Place
Tel: (204) 474-2323 ext 276                     Winnipeg, MB  R3T 1L7

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