In many email systems there is an undo send feature. Outside of those closed contexts where yanking a message out of the recipient’s inbox is possible, it is generally implemented by waiting a few seconds between when the UI says the message has been sent and when the message is actually sent. During that interval, an undo send option is offered which simply cancels the upcoming send action.
Yes, and those recall messages only exist in the closed systems where such retraction is possible, or in the open systems which send those messages that are more designed for the closed systems.
The implementation I described with a slightly delayed send doesn’t use those recall messages, since the email being sent doesn’t actually get sent until after the delay. I believe this is how Gmail’s version of the feature works, for example.
