Hi,

The people who answer questions here, for the most part, are other Firefox users volunteering their time (like me), not Mozilla employees or Firefox developers.

If you want to leave feedback for Firefox developers, you can go to the Firefox Help menu and select Submit Feedback... or use this link. Your feedback gets collected by a team of people who read it and gather data about the most common issues.

In 2012 Mozilla dropped priority for further Thunderbird development. and the code fell behind the "Firefox development curve" so some incompatibility has crept in.

On January 28, 2020, the Mozilla Foundation announced that the Thunderbird project would henceforth be operating from a new wholly owned subsidiary, MZLA Technologies Corporation, in order to explore offering products and services that were not previously possible and to collect revenue through partnerships and non-charitable donations.

For Thunderbird specific support and to ask about it, it is best to use the Thunderbird button in the lower-right corner of this support entry page. https://support.mozilla.org/en-US/ That will take you to Thunderbird support.