I'm currently playing around doing some development on an all-in-one box which is hosting web and mail services (among others), and I have a DNS question I can't seem to find a good answer to.
Imagine the domain here is example.com, and everything is running on a single host with a single IP (203.0.113.1)
For the website I have the following:
example.com. IN A 203.0.113.1 www IN CNAME example.com.
I know that MX record must not be CNAMEs (RFC 1034 3.6.2), so to set up MX for mail, the usual approach is to add:
mail IN A 203.0.113.1 @ IN MX 0 mail.example.com.
Now I'm wondering if I could instead just add:
@ IN MX 0 example.com.
However I'm not sure if there are any technical or RFC reasons that this isn't allowed/possible.