Firefox add-on that lets you add receipt request much easier.
Version: 0.12Toolbar button 'Return Receipt' adds in an easy way receipt request to composed message. After installing extension just go to customize toolbar window, drag 'Return Receipt' button and drop it on composed message window toolbar. Now you can very quickly and easily add receipt request. Highlighted button informs that request is enabled.
Operating System: Mac OS X
The Return Receipt Toolbar Button extension enables you to create a Return Receipt button to mail composition window toolbar.
Note: The Return Receipt Toolbar Button add-on is cross-platform and it works on Mac OS X, Windows and Linux.