I don’t know if this will make you feel better about it, but I don’t think this is really MIME or HTML. Ie: if I send myself a plain text email with an URL in it, then Thunderbird allows me to click it. In other words, nothing was actually encoded in the message, the viewer just recognized some plain text that looked like an URL and gives the option to click it. Even if I type: www. Random letters .com it displays it as clickable.

Thanks for the reply.

I do suspect that there is no way to configure TB to do what I want, to display email messages like what was done long ago when I used a dumb terminal for email.

I haven't have a chance to look at the full documentation and source code for TB. I gather the source code is some 6 gigabytes in size. I am still looking for documentation like a design specification for TB.

I suspect the a change to the source code is required. The issue is something like the choice of UI component from the Mozilla UI Framework (XUL) that is used to display the email message body text. The email message body text is stripped of HTML tags and the remaining text is displayed. The UI component acts like a micro web browser and If there is an URL in the body of the text, for example www.cnn.com , the UI component treats URL like an actionable HTML Link. Maybe there is another UI component that can be used to display the email message body..

It is unfortunate that security is an afterthought with the introduction most new technologies such as the use of HTML or MIME in email messaging. In the Linux disto Qubes OS it is possible to easily sandbox an email application to provide some protection from malware attack vectors in email messages but it is difficult to provide same functionality in Microsoft Windows because of OS licencing issues. Changing an application's behavior is an alternate option, in this circumstance. I do not think is a big inconvenience to have to copy/paste a URL into a web browser's address bar to view the web page associated with the URL. Maybe it will make a person take a second to think why they are doing the cut/paste of the URL in the first place from a security perspective.

Thanks.

This article explains how to make links non-clickable in TB by changing a preference:

https://askubuntu.com/questions/816609/how-can-i-disable-links-in-thunderbird