placing text such as https://support.mozilla.org/en-US/questions/1112715 in an email will see it "linkified" when you send the mail or save it to drafts. That has been a feature of Thunderbird since I think day on.e. It was certainly in Version 2

Sending mail in plain text should not have this feature.

Perhaps I should add, just as this forum turned the text I pasted into a link

Hi Matt, thanks for the reply. The problem with sending it as plain text is all images are gone too. I want to forward just without links, all the rest untouched.

The functionality seems to be there (Edit/Select All, then Format/Remove Links), it just doesn't work for me.

What style are the links? For example:

• Mozilla Support - display text is NOT a URL
• https://support.mozilla.org/ - display text IS a URL

What Matt is saying is that URLs in messages often are converted to links automatically either on the sending side, the receiving side, or both. So if the display text of a link you converted back to text is a URL, in most cases the recipient is going to see it as a link.

Is your goal to avoid the distracting appearance of links or to make them inactive and non-clickable? Do they need to work if copied and pasted into the address bar or would it be an option to inject hidden characters into them that break them?

The reason I asked is there were a few forwarded mails rejected recently by the recipient server, and I tracked the reason down to the links. Once I removed them manually, the mail went through.

Hmm, were you forwarding a message you received? If you hover your mouse over the problem links in that earlier message, were they direct to the address shown in the display text or did they connect through a tracking service? When they do not match exactly, some security filters could consider that to be an indication that its a phishing attack. Otherwise, it would be strange for a filter to refuse ALL links.