Re: IP as MX - should mail be delivered.

> A few times I've run across people putting IP addresses in as MX RRs for
> sites.

Err -- that doesn't make sense ....
An MX RR has a domain name, a preference value and a domain name.
You just can't put an IP address in there !

> Unfortunately from a customer support point of view, sendmail
> will actually deliver mail in this circumstance.

Can you give an example ?

Note that with most network services, the concern is that all (well, the
majority or RFC compliant) clients that you want to be able to talk to your
server can so do.

> I've dug through various RFCs and the all I can find is a place in RFC974
> where it says several places that an MX shall refer to a host name. i.e.

Sure should !

> However, I can't find anywhere that specifically forbids it.

That not the format of an MX RR !

> This makes it difficult when the customer is saying "but it works from my
> (other/old) provider"

Can you cite an example ?
I can't see how it can -- e.g. email from cl.cam.ac.uk will fail !

> Does anyone know why sendmail does support this

Does it ?

> and is there any reason to consider making exim do the same?

NO !

> My feeling is no, but as I say, it's a pain to try to explain to people
> why sendmail works and smail and exim don't. I haven't tried to see if
> qmail does or not.

Please give an example ...