Sorry should have said version 140.2.1esr (64-bit)

What font do you use? I really think it is probably something the council does not have, so it is being displayed with the next best character set they have.

I used to see it a fair bit when folk used windows XP era fonts (TTF) when the rest of the world is not using Unicode fonts. Things like Arial cause real issues like this as well as most of the fonts release with word processors before about 2016.

I have also seen it when folks use Apple specific fonts to send mail read on windows and when they compose in their word processor and copy and paste into Thunderbird to send.

HTML, which is how email is actually sent used a fallback process when fonts are specified. sometime the text has a series of fallback font listed, but that is generally when the professional have crafted a web site. Automatic fallback fonts can be ugly because the fallback is often to some default root, either san serif font or a serif font depending on which is specified.

This page contains some examples of user selected fonts and how they render in your browser. similar issues occur in email. All fonts are not "web safe" and my browser only renders about 2 of the cursive fonts listed as they are shown in the image. I know the issue is not exactly as you describe. but it does illustrate not all fonts work.

The same organization publish this page https://www.w3schools.com/cssref/css_websafe_fonts.php of web safe fonts and realistically you should keep you email to only those fonts as there is no guarantee when folk will see, but those can be assumed to be on most computers and phones, regardless of manufacturer or operating system.

Who is the W3C? In short The World Wide Web Consortium is the main international standards organization for the World Wide Web. Founded in 1994 by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working together in the development of standards for the World Wide Web. See the full Wikipedia article for additional detail. https://en.wikipedia.org/wiki/World_Wide_Web_Consortium

Thank you for your reply, I found that my email client was sending HTML as standard, I have now changed it to Text only using Ariel font. Just need to send a test message now. Thanks again

I am sorry, but text only had no font. That is the whole point of plain text, it has no formatting information of any kind associated.

You should be able to use HTML. I do, and so do most other people. The big issue is with the older TTF fonts, mostly that came with old versions of MS office that remain on your system but are not unicode fonts.