Hello Whetstone,
You should add a hidden field to your form. You will need to add JavaScript to the Initial JavaScript section in the Module Configuration -> Advanced Coding Options -> Custom JavaScript file area.
In this section, you'll need to provide JavaScript that will detect the browser that the user is using. Thankfully, no need to recreate the wheel, there's plenty of Scripts available on the web that can detect the Browser Type.
For instance, try this example:
http://www.w3schools.com/js/js_browser.asp So you'll need to assign the browser type value to the hidden field on initial page load:
$(NewHiddenField) = navigator.appNam + ' ' + navigator.appVersion;
The assigned value that will be assigned to the hidden field will be the browser name and browser version.
Now that you have the value in your hidden field, you can reference this hidden field value into your email event:
$(NewHiddenField)
Let me know if you have any questions.
Thanks,
Ryan