Problem
What is a "MX" record?
Solution
"MX" ("Mail eXchanger") records are used to specify what server on the Internet is running e-mail software that is configured to handle e-mail for your domain.
If you are using proFilter then you need to create the following MX records
MX 10 mxXXXXX.smtp-engine.com.
MX 20
mxXXXXX.smtp-engine.com
.
If you are using your own mail server remember to create the matching A record for that server and not a CNAME.