‘Undo Send’ is one of the excellent features we previously featured in Top Gmail Features for Teachers. Undo Send allows you to cancel a sent email immediately after it has been sent. What’s new today is that Google has finally made this feature available as a formal setting in Gmail on the web.Undo Send was first released in 2009 and since then it remained in Gmail Labs which is Gmail’s experimental lab that tests features to be added to Gmail official setting. Initially, Undo Send came with only 5 seconds interval time from the time you hit the send button till you decide whether you want to delay it or not. With this new update, Gmail now lets you choose between 5, 10, 20, or 30 seconds for cancellation period.To activate this feature, head over to Gmail, click on setting and scroll down till you find ‘Undo Send’ then tick ‘enable undo send’ and select your cancellation period.