Re: An A record is an MX record and is a missing MX....

MX records are only required if you want to have more than one mail exchange servers to serve your domain, e.g. if you want to have a secondary mail server as a relay if the primary server goes down.

actually, i suspect the more common use is that one has a collector server for a lot of local infrastructure, as in @ A 666.42.7.11 foo A 666.42.7.12 MX 0 @ bar A 666.42.7.13 MX 0 @ randy