Allows you to setup a system to create emails and schedule them to be sent at a certain time. You can compose them on any platform (eg. mobile/computer) and the only extra work is to apply a label and specify the time in which to send the mail.
http://code.google.com/p/gmail-delay-send/
Gmail Officialy Undo Send https://support.google.com/mail/answer/1284885?hl=en
others : http://www.boomeranggmail.com http://www.rightinbox.com http://www.labnol.org
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