If you've ever wanted to "Unsend" an email right after sending it, you are not alone. Wayne Gmail allows you to do this if you'll follow the steps below.
Open Wayne Gmail.
Click the Settings Gear in the upper right side of the page, and select "Settings".
In the General tab, scroll down until you reach the "Undo Send" area.
Set the send cancellation period to 30 seconds.
Thirty seconds is the longest period you can select to cancel a sent email. Wayne Gmail delays sending the message for 30 seconds. After 30 seconds, the message cannot be recalled.
After sending a message, you will notice the following message appear at the bottom left of your screen.
Message sent. Undo View message.
You can click Undo for 30 seconds at which time the message is sent and cannot be recalled.