[Greylist-users] Backup MX and forwards

Dave Anderson dave at daveanderson.com
Wed Sep 22 10:32:34 PDT 2004

** 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.)

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"?

[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.]

>The greater part of my spam comes through my UIUC address, which is
>forwarded, most frequently through university servers (for @cs.uiuc.edu
>and @uiuc.edu addresses) that send to a server I control, which then
>forwards to raeder.dk.  While I could greylist on my own server, the
>forwarding through university servers would make greylisting useless for
>those as well, right?

Again, since there's no direct connection from the originating server,
AFAICT you can't use greylisting.


Dave Anderson
<dave at daveanderson.com>

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