Mailto:

It makes mailto: links open in an online email service (webmail services).
Currently it supports AOL mail, Fastmail, Gmail, Hotmail, Yahoo mail and Zoho mail by default. You can also set multiple different email services yourself.

Compared to the other mailto extensions, this one can handle a lot more mailto links. Try out 

 for example (as far as supported by the email client of course). Also forms and javascript-inserted links are supported!

You can also choose to add an option to the context menu, to send the address of the page with your chosen email service. Furthermore, you can exclude certain web pages from this extension.