[Mimedefang] Checking SPAM first before virus

Kelson kelson at speed.net
Tue Jun 13 12:58:03 EDT 2006

Mathew Thomas wrote:
> Is it a good idea to check the SPAM first before checking the virus?
> Hope this can reduce some load on our gateways. What have I to do check
> the SPAM first on our existing installation without doing any
> recompilation?

Actually, you're probably better off checking for viruses first, then 
spam.  Spam checks tend to be much more resource-intensive than virus 

One optimization I'd suggest, if you haven't already done it, is to make 
sure you're using ClamAV via clamd rather than the clamav executable. 
That way MIMEDefang just connects to the daemon instead of having to 
load the entire virus database from disk each time.

Some other ideas for lightening your load: If you can find a blacklist 
that you trust, you can block some messages in Sendmail, before they 
even get to MD/SA/Clam/UV.  Check for forged HELO strings in 
filter_sender and reject senders who pretend to be your server.  Reject 
incoming mail claiming to be from your admin accounts in filter_sender. 
  Since you're running Sendmail 8.13, enable greet_pause, which will 
block senders that ignore the SMTP handshake.  Sendmail 8.13 also has 
some rate control and connection control features that will limit the 
number simultaneous connections from a given host.

Basically, anything *simple and reliable* that can drop junk before it 
gets to SpamAssassin will improve matters.

Another thing: SA 2.64 and MD 2.44 are both very old.  You might look 
into upgrading SpamAssassin (which will probably require a newer version 
of MIMEDefang), since you're basically checking for 20-year-old spam.

Kelson Vibber
SpeedGate Communications <www.speed.net>

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