Re: [Exim] 'Unrouteable mail domain'/sporadic MX lookup fail…

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Autor: Tony Earnshaw
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A: exim-users
Assumpte: Re: [Exim] 'Unrouteable mail domain'/sporadic MX lookup failures
fre, 2003-04-04 kl. 18:06 skrev Adam Newby:

> We've been experiencing a problem whereby MX records fail to be found for
> some domains when exim does a DNS lookup (NB as distinct from timing out
> when trying to do the MX lookup). In this case, exim appears to
> bounce the message immediately. This appears to be an intermittent
> problem, as the MX lookup is found OK with emails at other times.


> Can anyone shed any light on this problem:


What Exim version?
When receiving mail or sending it?

My 4.14 never bounces anything for this reason, but always gives a defer
- both on receive and send.

> 1. Could this be a problem with our local BIND installation? We run 8.3.x
>    rather than 9.x.


No way. That is, as long as your DNS is configured correctly and the
Exim server's resolv.conf points to it.

> 2. Can exim be made to retry in the event of no MX records being found?


In as much as Exim should give a defer, it already should do this. As I
said, mine does.

>    Looking at the source code, I'm not sure if this is possible without a
>    code change, but I may be wrong.

>
> Also, exim's behaviour in bouncing such messages immediately seems
> inconsistent. If it fails to find an MX record, it looks for an A record
> instead (for some reason!).


That's what it's supposed to do ;)

> For many people, this points at a machine not
> running a mail server, and often with a firewall, so exim attempts to
> contact it, and times out, causing the message to be deferred for retry
> later. If it happens that there's no A record, the message bounces.


It shouldn't bounce at all.

Best,

Tony

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Tony Earnshaw

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