The solution that we came up with for this issue was to create a WebHelp (in addition to the CHM) and put it on our company Website.
Then, the technical support right-click on the topic and send the path from the properties. (The URL in the address field is always the same address, since we use a parent-child Help.)
I know this isn't exactly what you asked, but maybe this will help.
You might find this link useful.
By clicking on a link in that topic, an email was created containing the text
"This page might help: http://www.grainge.org/pages/snippets/mailto.htm"
That text can be whatever you want.
See www.grainge.org for RoboHelp and Authoring tips
Two questions on the email link:
1. Is there any way to make the sendto email address user-entered, like through a pop-up? Your example appears to be hard-coded, correct?
2. Am I right in understanding that this would need to be added to each individual topic?