A feature of Thunderbird is that it sends plain text unless there is a style set, such as bold or underline. This is a feature not present in other email clients. However, when the Language Tool addon is used, it always triggers sending HTML text, overriding the user’s Thunderbird setting. I am referring to the setting in Thunderbird at settings>composition>sending format. The default is ‘automatic’, sending plain text whenever possible. Please fix this in the addon to allow the Thunderbird setting to function properly. Thank you.
Thanks for the report. I cannot reproduce this with TB 115.2.2, though. If I select “Only plain text”, the receiver will get a plain text email (tested with Gmail as receiver). Which version of TB do you use?