Working with Mail
To recall or replace a message you've sent, go to your Sent Items folder. Open the message you want to recall or replace. Select Recall This Message from the Actions menu. To recall the message, click Delete unread copies of this message. To replace the message with another, click Delete unread copies and replace with a new message, click OK, and then type a new message. To receive a notification about the success of the recall or replacement for each recipient, select the Tell me if recall succeeds or fails for each recipient check box. To replace a message, you must send a new one. If you do not send the new item, the original message is still recalled.
Remember, you can only recall or replace messages you sent to recipients who are logged on and using Outlook and who have not read the message or moved it out of their Inboxes.