add image.

''re :I downloaded and configured Thunderbird to use the 'English' spelling dictionary. '' When someone says 'English' to me, there is only one - English British, but I live in England, UK ''':)''' So 'colour' is spelt correctly for me. I believe the English speaking Canadians also spell 'colour' the same way. Do you mean downloaded English British, English United States, English Canadian ? I presume the downloaded dictionary appears in: Menu app icon > Add-ons > 'Dictionaries' Image shows: Menu app icon > Preferences > 'General' It looks like you have Thunderbird set up to use the 'English United States' for the general UI. Or perhaps you downloaded a version of Thunderbird specifically set up as English (US), so it defaults to that option? https://www.thunderbird.net/en-US/thunderbird/all/#E * Menu app icon > Preferences > 'Composition' * 'Spelling' section: * Language: What language is set up here as the default? In a Write window: On 'Composition toolbar' is 'Spelling', click on the drop down to see if you have additional dictionary which you could select.