Review for Outgoing Message Format by spidey9
Rated 5 out of 5 stars
It is annoying that this extension is even needed - it should not require an extension to simply change a default setting. However, there is no provision in Thunderbird for setting the default Outgoing Message Format to anything other than "Auto-Detect.
This extension provides that functionality, and does it perfectly. My heartfelt thanks to the developer(s).
To create your own collections, you must have a Mozilla Add-ons account.