Send mails with an expiry date(Outlook 2007, 2010)

               You send emails with a deadline such as invitations, etc. In such cases, you want the recipient to immediately see that the deadline has been overshot if he reads the email late.

               You can assign a validity date to your emails in Outlook. However this works only if the recipient is also using Outlook. For instance, this setting would be of no use if the recipient is using Thunderbird.
              In order to send emails with a validity date, compose a new message in Outlook. Then go to the "Options” tab. In the taskbar in the “Advanced Options” field, click the small arrow icon to open the “Properties” tab. Here activate the “Message valid up to” or the “Expires After” option under Delivery Options. You can set thedate and the time in the adjacent combination fields. Then “Close” the dialog box. You can now send the email as usual.
Note: The expiry date is valid in the overview of the sent items as well. Contrary to popular belief, the content and the access to the content remain valid even after the expiry date. Only the email is shown in gray and is struck out in Outlook. You can thus see at a glance that it is no longer valid.