North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: antivirus in smtp, good or bad?

  • From: Stephen J. Wilcox
  • Date: Tue Feb 03 09:49:41 2004

On Tue, 3 Feb 2004, Suresh Ramasubramanian wrote:

> Stephen J. Wilcox  [2/3/2004 7:28 PM] :
> > Whats happening is we're accepting the mail as the primary MX for the domain but
> > the user has setup a forwarding to another account at another ISP, they have
> > antivirus service on that other account. So we get the mail, spool it and try to
> > forward it but then we get a "550 Error: Suspected W32/[email protected] virus" after
> > DATA and our server freezes the mail.
> > 
> > Surely this is an incorrect way to do this as there will be lots of similar MXs 
> > like ours backing this mail up? They should accept the mail and then bounce it?
> Don't bounce.  Reject with 5xx during the SMTP transaction (immediately 
> after the DATA stage).  If you accept the mail and detect a virus later, 
> trash it instead of generating a bounce.

Ok I just realised what I'm doing here, 550 is a permanent fail and at this 
point as I am holding the mail on my server I should decide to return it to the 
sender. This isnt actually whats filling my queue and actually the reason I have 
some of these with 550 codes in the queue log is because they are bounces which 
means we handle them differently to normal mails and dont immediately fail them.

I'd mixed permanent and temporary, but thanks to rfc821 I've resolved my


> If you don't want to set up antivirus, at least set up Exim (preferably 
> with exiscan-acl) to reject mail with suspicious attachments.
> You might want to try the exim-users list for some more on this.