A response from an e-mail recipient that indicates the message was opened. The read receipt has to be requested by the sender, and the recipient may or may not comply. Although it is called a "read" receipt," there is no guarantee the person actually read any of the text. The message could have been opened and immediately trashed. E-mail client programs such as Outlook and Eudora support read receipt requests and responses, while Web-based e-mail does not. For automatic read receipts, see e-mail tracker.