Desperate cry for help: setting up MX records

[Alan M. Evans]

This is probably off-topic, so I'll be brief. (Really trying to avoid
subscribing to yet another list.) Somebody here must know.

My server hosts two domains. I've set up mail for one of those domains
and everything has been working for some time. I tried setting up mail
on the other domain without the slightest success.

I really need someone willing to hold my hand through the setup. If you
want to work it out on list then I could post more details, but like I
said, I think it's a bit off-topic.

Please! I've tried everything I can imagine. I've employed all the
google incantations. I'm generally a pretty smart guy, but this has me
floundering.