Boomerang lets you track if someone replies to an email and set reminders on important messages. According to the NY Times, it transforms Gmail into a (nearly) living, breathing personal assistant.
Note: If you are not a Google Apps domain administrator, please install Boomerang from www.boomeranggmail.com
Boomerang helps you focus on the most important messages in your inbox, when they're most important. It allows you to control when you send and receive messages at the perfect time, helping you stay responsive, close more deals, and feel at peace with your email.
There are 3 main features to help achieve this:
Response Tracking – Boomerang’s response tracking feature helps you remember to follow up with people if you don’t hear back within a given amount of time. We'll place the sent message at the top of your inbox if you don’t hear back within the specified time frame, alerting you to follow up with another email.
Boomerang Reminders - When you receive an important email that you want to check back on in the future, you can use Boomerang to remind yourself. This feature returns the message to the top of your inbox when specified. This helps ensure that the message is readily available when needed and reminds you to take action on messages when the time is appropriate.
Send Later - Using the simple “Send Later” button, you can schedule messages to send at a later time. The “Send Later” menu gives the option to choose from a set of common send times or specify the exact date and time that the email is to be sent. Without needing to log back in to hit “Send” or even have a network connection, Boomerang will automatically deliver the message at the desired time. (Note: only available through associated Browser Plugin)