Hello there There is no notification in Thunderbird for read mail or pop up in that program itself. At the moment in 2025 only by receiving mail inbox there is a that receiving notification on screen or monitor. The option to get a receiving notification for mail that has been read ,the option is to do by the receiver that can send you a receiving and read message back automatically so it is by the owner of the delivered mail. The question there is sended along in text to them to choose that yes or that answer to no. Most of all the other email providers do not cooperate with this subject to it at all. Greetings googlethunderbird.