Re: [exim] using MX always

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Author: Jeff Lasman
Date:  
To: exim-users
Subject: Re: [exim] using MX always
On Saturday 07 January 2006 06:07 pm, Giuliano Gavazzi wrote:

> ah, but this is a consistency nightmare! You should not allow them to
> use a domain identical to the domain they set up with you,


I agree, but if we did we'd lose business; can you imagine setting up a
hosting account and getting an error that you had to give us a
different email address? What if you didn't have a different email
address? We have to solve the problem.

> or, if
> that domain already exists you should not add that domain to your
> local domains until you have set up the dns for it (with MX pointing
> to you).


We set up the DNS before we send the email. The problem is we can't use
MX delivery or we'll have email loops. And also we have no idea when
the client will change their nameservers; that's not under our control.

> bad idea indeed, but it can be improved..


I agree that it's a bad idea.

> well, by definition the MX obtained from the DNS is not old...
> however can be stale if the queried server has got it cached.


By old, I simply meant on the server the client was and hopefully is
still using, until the account on our server is setup.

> You can achieve something similar to what you say this way:
>
> have two lists:
>
> local_domains = your permanent local domains
> customers_domains = your customers added domains
>
> then in the dnslookup router instead of
>
> domains = !+local_domains
>
> something like (in pseudo exim acl code, because it's too late):
>
> condition = {$domain not in local_domains} OR !{ MX($domain) =
> this_host }
>
> and the local delivery router uses
>
> domains = local_domains : customers_domains


Thanks; you've given me some good ideas.

> You must not add the DNS for the new customer domain until after you
> have sent the welcome message and the domain has been transferred.


But we're not sure when the domain is transferred, because the customer
does that. We're not in control of the Hosting platform in any event,
but we expect they'll make whatever changes we recommend, since we
write their exim.conf file and they want to resolve the problem as
well.

> I am not sure what !{ MX($domain) = this_host } evaluates to if there
> is no MX record (it can happen of course). There might be an option
> in the dnslookup to make it true. Otherwise just add the A lookup
> too.


If I decide to go this route I'll look into it, but I reallyl think the
easiest way to resolve the problem is simply to send the email out
using a different server.

Thanks!

Jeff
--
Jeff Lasman, Nobaloney Internet Services
1254 So Waterman Ave., Suite 50, San Bernardino, CA 92408
Our blists address used on lists is for list email only
Phone +1 909 266-9209, or see: "http://www.nobaloney.net/contactus.html"