Re: [exim] Retry on 550 errors

Dave Lugo wrote:
> On Tue, 5 Dec 2006, Marc Perkel wrote:
>
>>> Any MTA that allows an MX to decide whether or not a rcpt_to
>>> domain should be accepted, is a DoS waiting to happen.
>>>
>>>
>> Unfortunately I have no control over the other end. But that's how some
>> people set it up.
>>
>>
>
> 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.
>
>

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.