Perfect solution Rated 5 out of 5 stars

Wonderful! For years, when I've needed to insert graphics into Thunderbird emails which usually have not required alternate text, I have often forgotten to change the setting to "Don't use alternate text" in the dialogue box, and of course always got the error dialogue and so on. This add-on solves that problem and saves time. At the time I'm reviewing this, the version is 0.1, yet it already works perfectly! Thank you so much for this.