Re: [Exim] MX Record points to non-existent host

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Author: Willie Viljoen
Date:  
To: Greg Louis, exim-users
Subject: Re: [Exim] MX Record points to non-existent host
Greg, before you became the target of possibly uncalled for blogging and
flaming, I do believe you did raise a question, the answer is further down
in this post:

On Saturday 22 February 2003 15:38, Greg Louis wrote:
> On 20030221 (Fri) at 2220:03 +0000, Tim Jackson wrote:
> > The answer is in your post. Read Exim's (quite verbose) message again:
> > > all relevant MX records point to non-existent hosts or (invalidly) to
> > > IP addresses
> >
> > @ IN MX 0 209.239.13.194
> >
> > instead of (for example) something like:
> >
> > @    IN MX <pri> mail
> > mail IN A  209.239.13.194

> >
> > Therefore, puremetal.com do not have any valid MX records and in the
> > absence of them, Exim can't really do anything useful with the message.
> > If it's important, you could call them (puremetal.com) up and ask them
> > to fix their DNS. But you'll find if they actually like receiving
> > e-mail, they'll probably fix it soon enough anyway when they don't
> > receive half the mails they should.


> IMHO it ought to be possible to configure one's MTA to try harder to
> find a way through, even if that involves connecting to an IP address
> that doesn't have a reverse map at all.


I don't like this fact, but it is infact possible. Disclaimer: I can not say
how strongly I recommend that you not do this, but as I stated in a post to
another list earlier, it's a free world, and it's your right to use this if
you really feel you need it. This is from the specifications for Exim 4:

allow_mx_to_ip                  Type: boolean                  Default:
false


    It appears that more and more DNS zone administrators are breaking the
    rules and putting domain names that look like IP addresses on the right
    hand side of MX records. Exim follows the rules and rejects this, giving
    an error message that explains the mis-configuration. However, some
other
    MTAs support this practice, so to avoid 'Why can't Exim do this?'
    complaints, "allow_mx_to_ip" exists, in order to enable this heinous
    activity. It is not recommended, except when you have no other choice.


Again, I do not recommend this, but here it is.

Will

--
Willie Viljoen
Freelance IT Consultant

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