I have two mail accounts (say one private, one for business) in Thunderbird. Sometimes I mail (mistakenly) from the wrong account. That is, I read some mail in one account, followed by reading in the other account. I hit "compse" to send a message and forget to check that I am in the right account, the one I want to mail from. So, every now and then, I mail from the wrong account, get the incorrect 'sender' name and 'reply to' name in the message. I looked at account settings and found I can change the background color (in mails receivend and and sent and in mails while composing). I changed the background color in ONE account (to light yellow) and expected the other account to be unchanged (white). Not so. Changing the background color in the account settings for one account changes the color in all (both) accounts. This is both unexpected and undesirable and my problem is still there.