[mpclark]

It might be worth mentioning for those that aren't totally confident with DNS that (a) errors in setting up your DNS can take your services off line in unexpected ways (anyone else ever forgotten to put in an MX record and only realised three days later they weren't getting any email?) so be careful, and (b) at the low end one advantage of letting your host manage your DNS is that they can make changes behind the scenes -- for example, changing the IP of your website or moving your account to a different physical machine -- and they'll just update your DNS and everything keeps working. If your site is hosted somewhere like DreamHost but you put your DNS somewhere else, one morning you will wake up and find your site is no longer accessible and you'll have to remember that this is probably why.

[Dylan16807]

The RFC says that if there isn't an explicit MX record then it implicitly falls back onto the A record. But I'm sure many implementations screw it up.