Creating a Custom Access Key Email Template for App Tracker

Determine your App Tracker Site URL.
Navigate to Setup and search for Sites.
Record the Site URL for your App Tracker Site for use in your email template.
Create the Custom Email Template using CRM Email, making sure to insert the following URL into the email:

<<Your App Tracker Site URL>>/apptracker?id={!Contact.Id}&k={!Contact.TargetX_Base__Access_Key__c}

Note: The k variable refers to the Access Key, with the key value merged in dynamically.