Re: [exim] Retry on 550 errors

Dave Lugo wrote:
>>> Then all you can do is make them aware of the possible gotchas
>>> before cutover, so whatever they do is self-inflicted.
>>>
>>> You can probably prequalify them too: make some test domain or
>>> subdomain MX to the new customer's box(es), and then see if they
>>> blindly accept stuff sent to the new domain.
>>>
>>>
>>>
> On Tue, 5 Dec 2006, Marc Perkel wrote:
>
>> Many of these people have no idea what an MX record is. They have a
>> hosting company that does it for them. And the other problem is that the
>> MX takes time to propagate so the target server will work for a few
>> hours before rejecting the email.
>>
>>
>
> You seem t ohave misunderstood my suggestion.
>
> 1. Propogation delays aren't a factor for new records, only if
> you're changing a currently existing record, or the querying
> server has cached the NXDOMAIN.
>
> 2. YOU can add a subdomain of one of YOUR domains, and point the MX
> to the target.
>
> 3. If their box accepts based on MX, it should be ready to test seconds
> after you've pointed the test domain to them.
>
>

I think you're not quite graping the problem. The target server starts
rejecting email that it is not the lowest MX for. But if you change the
MX and it's in the cache of the target server then the target server
will continue to work thinking it is the lowest MX. So for a few hours
it works. Then the cache wears off and it realizes it's not the lowest
MX so it starts bouncing email.

Geberally the message is "You are not authorized to relay mail through
this server".