The enclosed was found in the mail or has been damaged in handling in the Postal Service (whichever is applicable to the enclosed).
We are fully aware that the mail you receive is important to you. Realizing this, each employee in the Postal Service is making every effort to expeditiously handle, without damage, each piece of mail with which the USPS is entrusted. Nevertheless, an occasional mishap will occur.
The Postal Service handles approximately 177 billion pieces of mail each year. It is necessary, therefore, that highly sophisticated mechanical/electrical systems be utilized by the Postal Service to ensure our customers prompt delivery of their mail. At times a malfunction will occur, the result of which is a damaged piece of mail.
We are constantly striving to improve our processing methods to that these incidences will be eliminated. You can help greatly in our efforts if you will continue to properly prepare and address each letter or parcel that you enter into the mail stream.
We appreciate your cooperation and understanding and sincerely regret any inconvenience you have experienced.
Sincerely,
Your Postmaster
This is the text on the outside of a clear plastic bag into which the US Postal Service places damaged mail--not only is it courteous and grammatically beautiful, but it contains several completely useless but nonetheless interesting facts. My favorite part, however, is that my postmaster regrets any inconvenience I may have experienced. Okay, my favorite part was that out of 177 billion pieces of mail, the USPS mangled my pre-approved credit card. | 
