On the menu, either * File menu * orange Firefox button menu there is an Email Link... item to compose a message with a ''link'' to the page. I don't think there is a built-in feature to send the ''content'' of the page. Perhaps you can find an add-on for that? (Some of the screen capturing add-ons do that, if you want to email an image of the page instead of the text.) Also, in case Firefox hasn't figured out that you want to use Thunderbird to compose the message, see this article: [[Change the program used to open email links]].