Re: [Exim] Delaying secondary mail exchange

Hi Kjetil, on Sat, 01 May 2004 03:46:34 +0200 you wrote:

> On Thu, 2004-04-29 at 22:54 +0100, Tim Jackson wrote:
> > b) find a provider who will co-operate in providing a backup MX with
> > strong spam-fighting policies and (at least) callouts to your machine
> > to reject recipients at SMTP time wherever possible.
>
> if the callout succeeds, why should the secondary accept the message?
> that server has no business talking to you if the primary is up.
<snip>
> the one failure mode this doesn't address is partial connectivity:

Which is exactly the reason why I personally wouldn't go as far as to say
"that server has no business talking to you".

> the server can talk to you, but not the primary, while you can talk to
> everyone. these days it's so common for spammers to go after the
> secondary, I'm convinced the upside of defering valid addresses is
> larger than the downside of not handling this split Internet situation.

It's an interesting idea, but I'm willing to bet that:

a) there is a significant amount of stupid but genuine software that can't
do MX priorities properly

b) this sort of thing would just generally cause problems, at least for
sites handling a significant volume of mail.

> qmail users can go stuff themselves...

Well, there's a reason not to do it for a start. However bad or good qmail
is (and based purely on the evidence I see rather than any careful
evaluation, I tend towards the former given the amount of collateral spam
generated by stupid qmail servers that appear to accept just about any old
junk and then generate bounces for stuff they don't like), there are way
too many qmail machines around to cause that kind of problem. Well, I
wouldn't do it anyway.


Tim