MX record and mail server question


I’m running a mail server on my home computer with sendmail. I have successfully set it up so email gets relayed to my ISP’s mail server “”. I have a few questions which I would greatly appreciate help with.


My computer running my mail server has an internal NAT address of 192.168.x.x that is supplied through a DHCP setting in my router. my external ip address is 70.71.x.x. I have setup my router to forward SMTP connections on port 25 to my mail server at 192.168.x.x.
My domain name is registered as

I want external mail to be able to send to any user on my domain and I need to set the MX record. When I send mail destined for external networks I have to relay the mail through my ISP’s mail server @ “”. What do i set my MX record as?? some info told me to set it as my ISP’s mail server, some told me to set it to my external ip address, and others said to use my FQDN, which I believe is in the format

does my FQDN include the host part in the name or is it just the domain? The computer hosting my mail server is, the “luke” part is the host name and “” is my domain name. Which if any do I use for my MX record?

The MX record value should be your external IP address which gets port forwarded to your internal server. If your external address changes then you need a dynamic DNS service to provide the MX.

Unless it is for learning purposes, it is not a good idea to have a mail server running like this.
If you really want a free email server, try google appplication services:
Google Apps