I find this kind of tool quite useful and am surprised at how rarely anyone develops such an extension. One extension like this I had stopped working (stopped being supported), probably having become incompatible with a new Firefox update. Another simply never worked in the first place and didn't (doesn't) even include a prompt for which email client you use. This one does though, and once you choose it ... in my case Gmail ... it works instantly.

Admittedly, it's less streamlined than the original one I used (the one that stopped working), because that one just wham bam sent the page no questions asked, be it from right clicking the toolbar icon or left clicking for a context menu. This one, however, lags to open a pop-up window for Gmail and then requires you to input who you want to send it to (such as yourself), but it does self-populate the subject line and places the url in the body of the message. The benefit of that is that you get to send the page to someone other than yourself if you wish ... instead of sending it to yourself first and then forwarding it to them once it arrives. No complaints. Five stars. Thank you Mr. Navas.