Re: [Exim] local_scan(), content-scanning, multiple recipien…

On Thu, 2003-02-06 at 19:54, James P. Roberts wrote:
> > The only other option is to have 2 boxes (or two MTAs on the same
> > box). The first one splits up messages into individual deliveries
> > that have only one recipient, and delivers these to the second,
> > which does the scanning.

But once you've accepted the mail, you have to bounce it. You _really_
want to preserve the property that if nobody wants the mail, you never
accept it onto any of your systems in the first place.

> That works, but could greatly increase the cost of scanning, since you'd
> have to scan (approximately) once for each recipient, instead of once
> per message.

Not necessarily. If you were using SpamAssassin, for example, you could
have the primary MTA do the scanning, and only look in the SA-added
headers to see which tests matches, and recount the _points_ for each
user, rather than doing the expensive part again.

In fact, since SA-Exim already has a complete list of recipients, it
could feasibly run SA once as it already does, but then perform the
calculation (and thresholding) for every intended recipient, then reject
the message only if _all_ listed recipients wanted to drop it.

It's not clear what you'd do if at least one recipient does want to
receive the mail -- you're lumbered with generating bounces for the rest
if you actually accept the mail, but there's probably not a lot of other
options. You can't reject it, and if you defer you'll only have the same
problem again later -- unless you can get away with something weird like
only accepting one recipient at a time from that host for the rest of
the day.

--
dwmw2