[Exim] Full marks to Exim :-)

Folks,

I've just discovered that Exim is even better than I thought: a domain I
tried to send mail to had the one and only MX record set to IP address
127.0.0.1. Exim rejected it:

>This message was created automatically by mail delivery software (Exim).
>
>A message that you sent could not be delivered to one or more of its
>recipients. This is a permanent error. The following address(es) failed:
>

>   XXX@XXX
>     It appears that the DNS operator for XXX
>has installed an invalid MX record with an IP address
>instead of a domain name on the right hand side.

I've obscured the actual address to save the blushes of the guilty, but
I've also emailed them to point out their error (nicely).

Regards,

Ruth