First, you must be composing in HTML for this to work. When doing so, there will appear a toolbar in the compose window where you can set bold, underline, special colors. Highlight the desired text and then click the icon on toolbar for bold. See attached . If that is not your intent, please be more specific.

This does not solve my problem. What I am after is similar to what you get when you highlight something to cut or copy but instead of carrying out that action I used to have a system where I could highlight something in an email the same as if done by a highlighter pen on paperwork and the section of email, when sent, would be highlighted and the recipient would se it as highlighted.

Aha! get the addon, textmarker. it does that for HTML messages, working just like a highlighter and you can set the color. Works very well.

Many thanks, David, but how do I get the addon textmarker.

Have now got the addon. Just trying to download it.

- click hamburger (three stacked lines) icon in upper right - click addons&themes - click textmarker in search window - install - after install, click the icon of a wrench in the description field and set to your preferences. l - then, whenever you click the 'new message' button, you will see the textmarker icon on upper toolbar for use. It appears whether you're composing in HTML or plain text, but only works with HTML message.

Many thanks. That appears to solve the problem.