Please describe in detail what you did so readers here may be able to advise.

Thanks, David. As I said, I think I accidentally put a very big value in for the top margin -- no idea what it was (just a slip of the fingers), but probably over 300 so that there was no space left at the bottom of the page. I don't know what else there is to describe.

I don't recall a top margin menu option. Was this possibly a config entry? That is why keystrokes did you do? If it was a config entry, you can find it by looking at prefs.js file in the profile and correct it there.

I went into File > Page Setup and set the top margin there, as I've done thousands of times before. I don't know what keystrokes I did -- as I've said, it was a slip of the fingers and must have been more than 300 because there was no space left at the bottom of the page. Certainly not a config entry and nothing to do with prefs.js. You are probably in USA, so I should have explained that 300 means 300 millimetres, the metric measurement we use here in Australia (and in most of the world).

My thunderbird does not have File>Page Setup, so I am confused. Are you referring to a Thunderbird menu?

Try this: Help/Troubleshooting Info, Printing (bottom of tab), Clear saved print settings, restart TB.

David, the first bit of information I provided in my first post was my Tbird version -- 78.14.0 (64 bit). In this version, Page Setup can be accessed via File > Page Setup or File > Print Preview > Page Setup.

sfhowes, thanks for the suggestion. I've looked in Help > Troubleshooting Information and have been right through it and searched for 'print' but Printing is not there. Perhaps it's only there in later versions? I'm using ver. 78 because it was the latest version that supports the extensions I want to use. But, later today, I'll check whether those extensions are now available in later versions and may update to a later version.