On Thu, Jun 28, 2012 at 07:30:02PM -0700, email builder wrote:
> example.com relay:internal.smtp.example.com
>
> * mail for example.com arrives at the relay because
> it is the highest priority MX record for example.com
Yes, but don't use the word "relay" here, it is too easily confused
with the transport name, calle it the border MTA or the SMTP gateway,
...
> * the relay is told by its configuration (see above) that
> internal.smtp.example.com is the next hop for mail
> to example.com
Yes, the nexthop *domain* is "internal.smtp.example.com".
> * so the relay looks up the MX for mail going to example.com
> addresses via internal.smtp.example.com and finds
> again that the MX for example.com is itself, creating the loop
NO. The MX lookup is for the nexthop domain, "internal.smtp.example.com",
that's where the mail goes, don't confuse recipient domains with nexthop
relays. If there is no explicit MX for this, the A record(s) will be
used instead.
--
Viktor.
