I don't know anything about the app mentioned in this video, bt it sounds as though ti fits the bill.
It is up to you to decide if you want to download and use it. It most likely makes chenges to the registry - so back it up first. The MAILTO protocol affects links for eMail on web pages and the filetype .eml is normally associated with an eMail client. I don't know if you can set a web basedclient to open local .eml filetypes
Anyway.... post back if you use this and let everyone know if it worked - thanks.