The easiest way to add Hotmail (now the Outlook interface) is using an add-on. This one has been mentioned by other users in the past:

https://addons.mozilla.org/firefox/addon/livemailer/

If you don't want any more add-ons, there is a manual procedure to add Hotmail/Outlook/Live Mail to the list of available mail services. I won't clutter this post with the lengthy explanation, you can read it here: https://support.mozilla.org/questions/1052976#answer-706235

This is what my settings look like

OK, I downloaded the Add-On. It appears to be installed. But there's still no "Windows Live" option, and nothing happens when I click the "Email Link" button. What is "WLMail" - is that in fact Windows Live Mail? It looks different than Fred's and it's doing nothing. Weird.

Hotmail is a popular program, why does it require an add-on and all this trouble when gmail and yahoo are just there by defaut?

Also, the add-on description says that it makes "mail to" links in web pages default to Windows Live Mail. It doesn't say anything, as far as I can tell, about adding Hotmail to the list in "Email Link" options from the File menu.

OK, the add-on didn't work. But I somehow muddled through Option 2 to add it manually, and what do you know, it worked! The most technical thing I've ever done actually I think. Thanks!

Is there any good reason to do the longer process in Option 1?

BlackberryPi said

Is there any good reason to do the longer process in Option 1?

No, unless Microsoft moves you to a new mail server. At that point, you would need to do either #2 again for the changed server or #1.

Great thanks much!