Is there any way to get Thunderbird to alert me that an incoming message has a return receipt flag on it BEFORE I open the message and the receipt is triggered? I work from home, and sometimes I'll look through my work mail late at night. However, I don't want customers to know I'm looking at mail at that hour; if I knew a message had a return receipt, I'd leave it until the next day. (Just blocking the return message from being sent raises its own red flags; I know there's no way to change the time that it reports.) However, I can't find any way of displaying that information, either as a column of the Inbox list of messages or in the message filters where I could color-code such a message. Any ideas?