Boomerang makes following up on emails much easier. It is a plugin for Microsoft Outlook that allows you to take a message out of your Inbox for a few hours or a few days, until you're ready to deal with it, keeping your Inbox Cleaner. Just right-click the message and tell Boomerang when to bring it back. When the time comes, Boomerang moves the message back into your Inbox, marked unread and flagged for follow-up. Boomerang can also automatically Detect dates and times in messages, suggesting related times for the message to return.
Boomerang is the perfect way to make sure you remember to follow up on messages later. It's also the lightest weight way to get started with GTD, Inbox-Zero, and other email management systems.