On 08 October 2002, Odhiambo Washington said:
> I was thinking about a user submitting an e-mail in the ordinary way, via
> an MUA.
With email, there's no such thing as "the ordinary way". There are
certainly Unix MUAs that work by invoking /usr/sbin/sendmail (or
/usr/lib/sendmail); there are others that work by connecting to
127.0.0.1:25. I don't know if there are MUAs that invoke "exim -bs" for
SMTP-over-stdin, but I wouldn't be surprised.
> 1. Sender A (some virus I guess) -> .exe file to userxx@mydomain
> 2. system_filter rejects and send the error mssg back (to some maybe non-existent address I think)
> 3. Remote server rejects the err mssg (because of possibly non-existent address still)
> 4. Rejection is sent to Mailer-Daemon/exim at mydomain.
Viruses should either be rejected at SMTP time or quarantined for manual
inspection. Attempting to reply to viruses is a waste of time, since
Klez -- the most common virus I see nowadays -- forges its sender
address. Replying to Klez increases the total amount of junk mail on
the Internet, so *don't do it*!
If you really absolutely positively can't think of any other way to do
it, though, your virus rejection messages should probably have an empty
envelope sender. That way, they'll be dropped rather than
double-bounced if they can't be delivered.
Greg
--
Greg Ward <gward@???> http://www.gerg.ca/
A man without religion is like a fish without a bicycle.
