Just above the text area that you use to enter the message text on the "Compose New Mail page" there is usually a button bar with buttons to add text formatting like Bold and Italic.
That toolbar may also have a button to turn a text link into a clickable hyperlink (look for a chain like button).
You can select the text and click that button to turn the link into a clickable hyperlink.
If you can't find the button then hover them all to check the tooltip of each (e.g. Insert hyperlink).

• Make Link - https://addons.mozilla.org/firefox/addon/make-link/

Thank you so much. Easy to follow and most of all - it worked! Well done.

You're welcome

This sounded really simple, but it didn't work. Might it be because the button only says 'link', it doesn't say 'hyperlink'? Whatever the reason, I still can't insert hyperlinks for the recipient to click on.

Libby -when you open the hyperlink, in the link box shown make sure you remove the 'http' already inserted if you are doing a 'paste' with an address that already starts with its own 'http' . I didn't with my first attempt which failed and I then noticed the address started with two 'https'. If you are typing in the link I guess you can leave the http shown. Hope I haven't confused you.

Did you select the link text before clicking that toolbar button?

I first copied the address I wanted to put into the Email. opened the Email page. clicked on the hyperlink. deleted the existing 'http', did the 'Paste' then clicked on OK. The address then appeared underlined in the Email and ready for clicking on by the recipient.

It worked for my updated Outlook (MS Office 2011)! Thanks

Thanks so much, I've been having this problem for so long now. Yours is the only solution that makes it clear how to solve it. Still don't understand why it doesn't work automatically in Firefox as it does in IE but hey it's not a big hardship.....and it won't make me start using IE again!! Cheers