User Manager Email Template

I like the user manager sending an into email upon creation of the user account. The variables however are a problem. Specifically, the template is inserting my servers ip address in the template where I need a dns name instead.

i.e. http://44.44.44.44:81 should look like http://pbx.mydomain.org:81

Our dns names resolve properly from inside and outside but the IP address from the template is only our external IP.

Is there a way to set the variable used for creating this?