Rather than trawling through the RFCs, I thought I'd be lazy and ask here instead. ;)
I have a domain for which the primary purpose is to catch typos for an important email address - there's no associated website. I set up the DNS with the usual SOA record, two NS and 7 MX records (plus a CNAME for validating with Google Apps).
Do I actually have to add an A record to the DNS, or is just having MX records valid?