announced today a new feature for the Google Apps for Business and Google Apps for Government versions of Gmail: read receipts. If enabled by your Google Apps admin, you can now monitor the read status of sent e-mails.The Google Apps team
This brings Google Apps a little closer to feature parity with Microsoft Outlook, which offers a similar feature.
Here's how Google Software Engineer Carl Haverl explains it:
Read receipts allow senders to monitor the status of the messages they send and allow recipients to acknowledge receipt of mail. Let's say John works in sourcing for his company and wants to make sure that his suppliers receive his purchase orders. As he sends each one out, John can request a receipt and later check that the recipients have received the orders. Conversely, if someone sends John a message with a request for receipt, Gmail can send a receipt to the sender when John opens the message. Read receipts work both internally within your organization and externally, so they can help improve communications with customers and partners.
Automatic receipts will only be available within the same domain. Admins can choose to enable manual receipts but leave automatic receipts disabled.