Hello there Yes I did read your message , no there is no built in Thunderbird message or sound message by or getting sending that message as in Outlook where the message ringer or reminder of returning that message quickly can be chosen in the program and thereby you can react by stopping that sending one message to the receiver of that message. There is for receiving that message a noise to if some incoming messages are there. Or for receiving that sound or notification or stop message pop up for having send that message permanently. In Thunderbird you can choose that ''message delay function'' that hold's down a message in the message outbox folder. also you can hold a message there manually for a while by yourself and then try to choose for it. So you can create a sort of holding that message aside for a while before you think of sending that message. Just as the delay function it holds that message there in that same mailbox outbox folder before further sending that message. email programs can have these good sound functions and other email clients or providers can have normally other cool functions. Greetings googlethunderbird .