Boomerang
Gmail Extension
See who has read your emails, schedule an email to be sent later, or schedule a recurring email!
What Boomerang Can Do
You can "boomerang" it. This means that you will get an email in the specified time frame if the recipient has not replied, clicked, or opened the email. This return email can serve as a reminder to you to contact that person again, if needed.
You can also schedule emails to be sent later. For example, if you are composing an email on Friday afternoon, but you know it will not be read if it is sent out then, you can schedule it to go out Monday morning!
Note that you can also schedule a recurring message!