After clicking the print icon to launch the printable version of the message in a new window or new tab, you can cancel the print dialog and use the Print Preview feature. This should help reveal whether there is some peculiar scaling applied to the message and let you adjust it. Can you track down the issue?

Thaks Jscher. When I took your advice I found that the scaling was 50%. When I increased this to 70% the font size increased but I could only fit the whole text on landscape. Is there any way round this? DC

Unfortunately, it depends on the layout of the message, just like any other web page. If the author formatted it for a fixed width, the only way to make it fit without ruining their design is to shrink it down.

To modify the design, you could try an extension like Print Edit. I haven't used it for a few years, so I don't recall how well it addresses this problem.

https://addons.mozilla.org/firefox/addon/print-edit/

Thanks JScher. I'll try it. Best wishes

i think , you should check all the options while you are clicking the print menu , because there are a lot more options to match up your choices.