You can do MX lookup via:
1 open a command prompt
2. type nslookup and enter
3. type set type=mx and enter
4. type the name of the domain for example chipwebster.com and return
Or you can use web based tools such as:
http://www.mxtoolbox.com/ok how have you setup the MX record?
For example you should be creating a sub-domain called mail.chipwebster.com and setting the IP to the correct IP of your public interface of the firewall / security applicance
you then change the MX record of the domain chipwebster.com to mail.chipwebster.com and the cost i.e. 10