Boomerang for Gmail

Boomerang for Gmail is a Firefox, Chrome and Safari plugin that lets you take control of when you send and receive email messages.

Features

• 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 message as you normally would, then click the Send Later button. Use our 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.
• 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 the message. At the time you chose, we'll bring it back to your inbox, marked unread, starred, or even at the top of your message list.
• 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.