The latest version of PADS augmented with FreePBX code,, has an updated warp system tools module. This module now includes a page that allows you to configure the ssmtp email server on the WARP. You can see a picture below:

All you need to do is plug in your email servers name or IP. If it requires authentication then you can enter that as well. The final field allows you to tag the name of your WARP appliance so emails will appear to come from it.