I set up an MX record and my mail doesn't work, why?
The most common mistake is to set up an MX record, without setting up an IP address for the mail host.
For example you create a MX record called mail.example.com for the domain example.com but mail.example.com has no IP address
It's important to create an address record for mail.example.com aswell.
Note this record must be a A record and not a CNAME to another record.