Do you know it is better to send a v2 rather than recall the email, see SSW Rule Do you know when and how to send a v2 of an email?
Even though you may check your emails before sending, use SSW lookout to help you avoid mistakes, and even if you send/receive manually, there will still be times where you will send out an email with mistakes or incorrect content.
But all is not lost.
With Outlook 2007
If you go into your sent items, open up the offending email, and go into Actions | Recall this Message, outlook will attempt to delete the message from the recipient's inbox before he has a chance to read it.
With Outlook 2010
If you go into your sent items, open up the offending email, and go into file | Info | Resend Or Recall | Recall this message, outlook will attempt to delete the message from the recipient's inbox before he has a chance to read it.
Figure: File | Info | Resend Or Recall | Recall This Message (Outlook 2010)
Outlook will tell you whether it was successful or not
