Re: [Exim] FIY: Turn off virus alerts to sender (slightly OT…

Calum Mackay wrote:
>
> Pat Lashley wrote:
> > No, this doesn't bounce the message, it blocks it at SMTP time with
> > an appropriate error code. That is -exactly- the right thing to do.
>
> Ah, I'm relieved. Ignore my other emails...
>
> So some people actually send out-of-band reply emails, to the sender, in
> additional to denying the original in the ACL?

I'd say it's not so much an issue of "in addition to denying the
original in the ACL" but a case of accepting everything at SMTP, and
then only later figuring out that it's malware or a nonexistant user. A
ton of sites don't do any checking during the SMTP DATA phase -- this is
one of the unique features that brought me to Exim.

Once you accept the message at SMTP time, you're responsible for either
delivering it or generating a bounce, by classical logic at least. So
if you accept everything and only then scan later, you're left with a
quandry of either discarding the message or generating a bounce. The
key factor of scanning at delivery time is you don't accept
responsibility for it if you deem it to be crap.

I think a lot of "middle management"/decision-maker types are uneasy
with the thought of an email getting lost ("What if we send our client
an important email and it's silently dropped!") and so they want bounces
for everything. Couple this with malware/AV software that comes by
default with the option enabled -- perhaps as an underhanded form of
advertising its effectiveness -- and you have the current storm of
undeliverable-notification-malware-spam.

Brian