I have NUMEROUS email accounts in Thunderbird, and when composing emails I occasionally find myself in the uncomfortable situation of sending the email from the wrong account - this happens because the From address is prepopulated and I occasionally forget to change it. Is there a customization or add-on that ensures forces that field to be initially blank when the Write Email dialog is open, thereby forcing you to select the From address before sending an email? This will ensure that I am consciously aware of the email I am sending from instead of sending from the wrong account when I click send without checking first.