Script Summary: Makes mailto links open cleanly in a Popup GMail window - Google Apps or Regular GMail
This script has been written to be very fast and won't clog your pages down. I tried a lot of other GMail scripts and were massively OTT, plus none had decent popup windows.
Note: This will work with Google Apps or regular GMail - Look for this line:
window.GMAILTO.domain = "yourdomain.com";
Either set your google apps domain, or comment it out for regular GMail!
Peace, patience and respect,