Many times we wrongly send mails, that leads lot of problem, to avoid the google provides a undo send option to recall your sent Messages within few seconds after you second. It is like a “recall a message” in outlook. Undo send message is part of GMail Labs, you have to login to GMail Labs to enable this option. Gmail Labs is a testing ground for experimental features that aren’t quite ready for primetime
Click Settings on the top right corner of the GMail, goto Lab Tab and Enable “Undo Send” Option to enable in gmail. Green color container symbol at the top right corner shows GMail Labs feature is enabled.
You can notice “Undo” option, whenever you 
send any mail .we have to click just “Undo” before 30 seconds to recall your mail.
send any mail .we have to click just “Undo” before 30 seconds to recall your mail. In outlook, when you recall your message, the user is notified with an message that message is recall by this person. There is no symptoms of the person sent mail to X person.