Send a message to yourself. Or save your message as a Draft and look at it in your Drafts folder.

I'm pretty sure that anywhere other than the Composition window, valid links for both email and URLs will be shown as active, clickable links.

If you want to dress up a link so that it looks like this and not like this: https://support.mozilla.org/en-US/questions/1209676 then use the Insert|Link option in the composition window's menu. Note that while it is configured for URLs, it can be used to form mailto: links for email addresses. So you could generate a link that does this:

Contact me!

…which will (or should) launch the recipient's email client.

Thanks very much. Problem solved. I'm also trying to import my address book using vCard files but I can't 'select all' and do it in one go. Too many to do individually. Isn't there an easy way for Thunderbird to collect addresses from Window LIve Mail address book? Thanks for your help.

I don't have much experience with Microsoft's email programs, so I can't help you there.

You'll get more attention if you ask that question in a new thread.

OK Thanks.