If you mail a letter USPS Certified Mail the Post Office provides the mailer with (2) mail receipts.  The first certified mail receipt is many times described as ‘proof-of-acceptance’ this is a receipt from the Post Office that they accepted your letter on a specific date and time to prove your letter was mailed.  The second is referred to as ‘proof of delivery’ 

When you mail a Certified Mail letter you may need proof that you mailed the letter timely as well as evidence of delivery (to whom the mail was delivered and date of delivery), along with information about the recipient’s actual delivery address.. 

Certified Mail forms are available free from the local Post Office.  If you are mailing more than 3 items USPS suggests using a ‘firm sheet’ or manifest (PS-Form 3877).  This special certified mail receipt is printed using computer software and was designed to help large volume mailers that send lots of USPS Certified Mail.  The software insures the USPS Certified Mail article number is correctly listed with the accurate delivery address for each recipient with the unique article number for each piece of Certified Mail.  Additionally all USPS special service fees including the certified rates and costs, first class postage and additional endorsements are correct according to USPS standards.

When you take your letters or articles to the Post Office window clerk or Business Mail Entry Unit (BMEU) make sure they round stamp (date stamp) and sign the firm sheet or PS-3877 manifest. This becomes your receipt and legal proof of mailing and acceptance of your letter into the USPS mail stream.

No other paper receipt will be provided by USPS unless you are using the Electronic Return Receipt that provides electronic tracking and delivery confirmation service.

Other Related Certified Mail Questions:
What happens is my Certified Mail Letter is not delivered?
How can I get proof I the Certified Mail letter was delivered
How can I get proof I mailed a Certified Mail letter

To learn more about USPS Certified Mail automation contact Certified Mail Envelopes at 800-406-1792, sign up for the free trial and get 2 Certified Mail Envelopes with Electronic Return Receipt to try for free.