[Wylug-discuss] Secondary MXs and NDRs

[Andrew J Cole]

I have long used DynDNS's MailHop Backup MX service which is configurable
to support the same DNS tactics and RBL lists which I use on the primary.

Well very nearly if only they would keep a closer eye on changes to RBL
lists and adjust accordingly.

I have no doubt that they see lost of spammer traffic which reies to
relay through the secondary on the assumption that the filtering is
weaker on that route.

My niggle aside their service works very well.

A couple of weeks ago they decided to stop delivery of any
locally-generated NDRs from their systems.  Of course this only applies
when/if delivery to the primary is not possible (otherwise they do reject
delivery using SMTP call ahead).

This, of course, goes against a MUST in Section 3.7 of RFC 2821.  They
rationalise this in several ways, by saying that the RFC was designed
for the time when both servers and backbones were much less reliable and
that they follow most Internet Standards but in this case individuals
(spammers) are already breaking the rules so ...

My main concern is that this does nothing (very much) to reduce traffic
and somewhat helps spammers by diverting attention from NDR blow-back
(of course it somewhat hinders them as well if they are relying on NDRs
to trim their lists).

Discuss.

Andrew