Boomerang - send an email later

With Boomerang, you can write an email now and schedule it to be sent automatically at the perfect time. Just write the messages as you normally would, then click the Send Later button. Use the handy calendar picker or our text box that understands language like "next Monday" to tell Boomerang when to send your message. We'll take it from there.
NOTE: The FREE version will allow you to schedule 10 emails per month, you can do more but will cost $$$$$$
Remind you if you don't hear back
There are times you need to make sure you follow up within a specific time frame after sending a message. You can select to only be reminded if nobody replies, or regardless. This way you won't let messages slip through the crack and will never forget to follow up with people.
The best follow up reminders
Want a cleaner inbox, but don't want to lose track of important messages? Use Boomerang to take messages out of your inbox until you actually need them. Just click the Boomerang button when you have an email open, and choose when you need it again. Boomerang will archive your message. At the time you choose, we'll bring it back to your inbox, marked unread, starred or even at the top of your message list.
How to Send Later with Boomerang for Gmail 
How to Track Responses with Boomerang 
How to Schedule Reminders with Boomerang 
Adding Boomerang to your Gmail Account.
1. Sign In to your CEO Google account

2. Visit the Chrome Store: https://chrome.google.com/webstore
3. Search for Boomerang and add the App to your account.

4. Now when composing a new email you will see a series of new options.