When a message is sent (or saved as a draft), Thunderbird 'activates' links in the message, adding formatting as necessary and making them clickable hyperlinks. When links are 'activated', they are difficult to edit (because when you try to position the cursor within an active link you usually launch the link in the browser). If you paste or type a link into the body of a message it appears in the text of the message without any indication that it is a link. command, the link is formatted as a link (underlined and colored), but if you click it nothing happens. Unlike some other email programs, Thunderbird does not create a clickable link when you are composing a message and add a hyperlink. 2.4 Check for interference from an extension.2.2 Check that no application is specified for the HTTP content type.2.1 Check that the operating system's default browser is specified.2 Problems with received or saved mails.