[Greylist-users] Backup MX and forwards

[Lars Clausen]

On Wed, 2004-09-22 at 19:32, Dave Anderson wrote:
> ** Reply to message from Lars Clausen <lc at statsbiblioteket.dk> on Wed,
> 22 Sep 2004 16:33:57 +0200
> 
> >My current mail server raeder.dk is behind a backup MX system that my
> >ISP requires, blocking SMTP from all other hosts.  This is common in
> >Denmark as a measure to... decrease spam:(  This would make greylisting
> >at my current server impossible, yes?
> 
> Since greylisting depends on having a direct connection from the
> originating server, yes -- the enforced detour through your ISP's
> server prevents you from using greylisting.  (But I am not an 'expert',
> so be sure to have this confirmed by one.)

Seems to be confirmed by now.  Bummer.

> I am curious as to how routing _incoming_ SMTP connections through
> their server is supposed to reduce spam (other than subjecting you to
> whatever spam-filtering the ISP chooses to impose, AFAIK there's no way
> that it can); does your ISP give any explanation, or is this yet
> another case of "we _know_ that no mere user could possibly understand
> this; don't bother us"?

At least TDC and Tele2, two of the major ISPs here, do that.  It's
annoying to set up and makes several useful things like real backup MXes
and, I see now, greylisting impossible. 

> [Forcing _outgoing_ SMTP connections to go through the ISP's servers is
> a different matter, and makes sense in many cases -- though it does
> interfere with some anti-spam measures, such as SPF.]

That, on the other hand, they don't do.

-Lars