> >># host mail.example.com
> >>mail.example.com is an alias for hostname.example.com.
> >>hostname.example.com has address 1.2.3.4

> >
> >
> >Wrong. The MX record has to point to an A name, not a CNAME.


On 22.10.08 21:21, Len Conrad wrote:
> what?
>
> MX record's data field is a domain name
>
> That domain name owns one or more A records.
>
> With mail, the shortest resolution path is always best practice, and
> resolving through a CNAME is not the shortest.


Isn't that exactly what Joseph Brennan said/wrote?

> Similarly, an MX's IP should have only one PTR record, whose domain name
> in the data field "matches" with an A record:


This is not so important, unless they are used for outgoing mail.

I don't know of anybody who checks for validity of reverse RRs of named MX
records point to (why to check that? to refuse delivering mail to provided
address? what will it tell the sender?), and I know of domains where MXes do
not have PTR records and nothing happens.

> d.c.b.a.in-addr.arpa. PTR label.domain.tld.
>
> label.domain.tld. A a.b.c.d


This should apply for everyone who wants to use any remote services, which
is not the MX case (the MX indicate inbound, not outbound servers).

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