Re: [EXIM] Avoiding a bad backup MX server

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Author: Peter Lister
Date:  
To: Peter Lister
CC: exim-users
Subject: Re: [EXIM] Avoiding a bad backup MX server

In summary, the answers I've received on the list and privately are
variations on...

1 Set up a specific route for one2one.net
2 Set up some sort of local DNS / naming hack to which a local user can
forward to achieve the above
3 Ignore MXs above a certain threshold
4 Firewall the pipex server

All of which are system hacks that I'd really like to avoid for the
reasons stated (the main one being that if one2one DO eventually get their
act together, we won't see the changes).

The user himself has tried to forward to <alias>@mail1.one2one.net (nice
try, didn't work), and writing perl to attempt delivery to only mail[12] -
He didn't know about the perl Mail modules, so he didn't get very far. If
it continues to be an issue, we'll probably set up specific routing via
a local-access-only alias (e.g. 121.sychron.com); this means that he can
set up his email to be forwarded to this, and we don't break the "real"
one2one.net in the long term, and he can switch back when (if) one2one get
their act together.

He did ask pipex (who do answer postmaster) about their view of this;
predictably, they are acting as a backup queue for one2one, and their
queue is simply trying to deliver to one2one as well - the reason it takes
24 hours is that it takes that long for one2one to cope with the backlog.
This email service is designed to go via SMS to a mobile phone, and so
one2one must strip out vast quantities of headers, attachments etc, and
probably reject many. I'm wondering if it's this which is causing the
backlog.

It's worth reinforcing the point that pipex appear not to be the guilty
party here: I would not consider firewalling them out. Quite apart from
the difficulties of doing that reliably we may accidentally nuke
legitimate access to that server which may serve other email domains.

Of course, if we retry more frequently, we'll just be clogging up the
one2one servers with that many more connections - presumably one2one are
using pipex *precisely* to reduce the server load, and the number of
simultaneous connections. If one2one are having capacity problems, then it
would make sense to route *all* their mail via pipex, so they only have to
receive email from one "client".

So, if any of you are looking for a new job, consider sending your CV to
one2one, as they clearly need a clued postmaster.

Peter Lister         P.Lister@???    PGP (RSA): 0xE4D85541
Sychron Ltd          http://www.sychron.com  PGP (DSS): 0xBC1D7258
1 Cambridge Terrace  Voice: +44 1865 200211
Oxford OX1 1UR  UK   FAX:   +44 1865 249666



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