User Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.7 Safari/537.36

Steps to reproduce:

When creating a reply, forward, or new email the default position of the cursor is in the to: address box and not in the body of the message.

Actual results:

When I created a reply to an email I began typing and enter a portion of the begining content of my email into the to: address box.

Expected results:

I would expect that when creating a reply or forward the default cursor position would be in the body of the email, so when clicking the "reply" or "forward" button you could begin typing your message or thought imediately. This is my native reaction when replying/forwarding emails.

I can see the argument for having the default cursor position in the address box on new email creation. When creating a new email, the receipient is at the forefront of the thought process in most cases, and then the message. In a reply it's the opposite, you've commited to sending a response to the email so the initial thought is the message. One might say that is the case with forwards, sure you might have a receipient in mind but the message, probably takes precedence in that case.

Overall it is definately worth looking at the default action in this case.

I can confirm this using Mozilla/5.0 (X11; Linux x86_64; rv:73.0) Gecko/20100101 Thunderbird/73.0a1 Build ID 20191212095840 with the new composition window.