Go to the Sent Items folder in Outlook and open the message you want to recall.
Tools menu-->Click on Recall This Message
If your message hasn't already been opened by the recipient, either delete the message or replace it with a new message.
if there are multiple recipients, you can request notification of whether the recall succeeded or failed for each one (at least you'll know whom to apologize to). Even if you successfully recall a message, the recipient may still know that you sent a message and then recalled it. So if you didn't replace it with a corrected message, you'll need to get your story straight as to why you recalled it.
