Inserting a Link in HTML
You can insert links into the email:
Select the text that you want to turn into a link.
Either click Insert ▸ Link… in the menubar, or right-click on the selected text and click Insert Link.
Digite o endereço no campo URL.
Click Close.
Alternately, you can also use the icon in the second bar below the Subject line.
If you do not want a special link text you can just enter the address of the link directly. It will be automatically recognized as a link.