Re: [exim] two stage virus scan

On Sun, Jun 18, 2006 at 10:59:07PM +0200, Marten Lehmann wrote:
> Hello,
>
> > is really a bad idea to send a bounce message for viruses, almost all
> > sender addresses are faked and you get the risk to be blacklisted by
> > other servers.
>
> but what happens to false positives (which should be very rare)? Then neither
> the sender nor the recipient knows what happened to the mail.

suppressing bounce messages is a stupid idea; blacklisting
hosts for sending bounce messages is an equally stupid
idea (actually blacklisting is foolish anyway, for obvious
reasons, but inexplicably it is popular). Unfortunately
these two different forms of stupidity have not cancelled
one another out so you have to work around them. The usual
solution is to sacrifice an IP address to the sending of
bounces (use `interface = ${if eq{$sender_address}{} ...}'
in a transport); this will be blacklisted by the idiots,
but at least at that point they have taken a positive
decision to prevent their users from finding out whether
their email gets through or not, and therefore you are no
longer contributing to the growing unreliability of email.

Of course, this is not a good long-term strategy, because
the supply of IP addresses is limited whereas the supply
of idiots is not, so sacrificing IP addresses for special
cases in this way is unsustainable; but hopefully one day
IPv6 will come along and solve this problem for us.

--
``The practical scientist is trying to solve tomorrow's problem with
today's computer; the computer scientist... often has it the other way
around.'' (from `Numerical Recipes in C')