YOU CAN RETRIEVE A LETTER

Perhaps you wrote something that you shouldn't have or perhaps you slipped the wrong item into the wrong envelope.  You cannot recall email but you can try with regular mail.

Utilize PS Form 1509, Sender’s Request for USPS Package Intercept Service - more information can be found here:

http://about.usps.com/postal-bulletin/2012/pb22329/html/updt_005.htm