I'm totally fine with setting up sub-domains etc when managing my domain but I've recently been asked to direct all mail for a domain to a particular exchange so people can retrieve email for the domain using their normal email addresses (on a different domain) and I'm slightly embarrassed to admit that I'm not really sure what to do.
The situation I'm trying to get to is:
Website is at: www.mydomain.com
Any mail through the site sent to e.g. firstname.lastname@example.org, email@example.com needs to be sent to firstname.lastname@example.org and email@example.com.
Now, from my limited understanding of the way email works in DNS my reckoning is that I can set up an MX record that points to the IP of their mail exchange. Then they can set up aliases to check for firstname.lastname@example.org and direct it to email@example.com. Is this correct?
If so, how do I set it up? If not, what do I need to do to achieve this result?