Hi - this question was about the opposite - someone wanting to turn off preview and print direct. Check the setting mentioned - in case yours is 'false' then set to 'true'. https://support.mozilla.org/en-US/questions/1357571 Same message mentions workarounds, and that changes are coming, so your version of Thunderbird may have different options.

I'm afraid this setting is already on 'true' (but thanks for your help anyway)

You mention : I'm afraid this setting is already on 'true' But that would mean you should see 'Print Preview' I had default setting: 'print.tab_modal.enabled' = 'True', so I would get the 'Print Preview' screen.

This allows me to check all is ok and choose printer - although beware...the developers of Firefox seem to use the very odd choice of words - they use 'Destination' which basically means 'Select Printer'. (Thunderbird have been forced to use the firefox coding - so obviously it going to need a serious fixing to adapt for Thunderbird users)

When I changed setting 'print.tab_modal.enabled' to 'false' then right on email and choose 'Print', I am now offered the 'Print' screen - see below. The first thing it asks is 'Select Printer'. Although the last printer - my default - is selected, I do have the ability to choose another.

Perhaps you have another setting which is forcing you to by-pass both the 'Print Preview' and the 'Print' window.... Check this setting in the Config Editor: 'print.always_print_silent' If it is set to 'True' then set to 'False'

Great! However your first solution didn't work (print.tab_modal.enabled), the seconds one does (print.always_print_silent)! Suddenly the cause of this problem occured to me: I'm pretty sure it comes from the addon 'FiltaQuilla', which I recently installed. This addon adds the option of direct printing in filters. Thanks for your help!