Rated 5 out of 5 stars

This is one of the most useful add ons. Thanks!

It seems the latest version has made some changes and doesn't feel as intuitive as before in these 2 places:
1. "Send at" , which I believe used to be a calendar widget
2. I somehow keep saving to Outbox when I tried to save to Draft for sending later... eventually I got it done correctly.

This review is for a previous version of the add-on (7.3.4). 

1. You need to enable the Lightning add-on to get the date/time picker widgets back. This is due to a deficiency in version 68 of the core Thunderbird application.
2. The UI hasn't changed since Thunderbird 60, so I'm not sure why you're clicking the wrong button more often now than you were before.