Post dating an email
For how to search email by a certain date range question in Outlook, this tutorial will give you all the instructions.
Currently Boomerang extension is available on invitation only. Random Time Choose any option as per your convenience and schedule the email message for that time period.
As there is no default option in Gmail to schedule an email for future date and time but now using Boomerang, you can schedule email on Gmail and do many more thing as well.
Boomerang for Gmail is an extension for Google Chrome and ad-on for Mozilla Firefox which enables users to schedule emails on Gmail for future date to send that later.
A handy feature missing from email services is the ability to say when an email gets sent - you must click the "send" button at the exact moment of delivery.
With this service, you can write emails with your existing email address, and they will get sent at the exact date, or dates that you specify - down to the minute.