>> * 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,
OK thanks for the language tips >> * 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. I see. So the MX lookup will be specific to the exact domain with hostname, etc. So MX load balancing would in fact work here. Although the suggestion to disable MX lookups and use A-record load balancing for the internal SMTP servers looks like a good idea Thank you
