Keyline —Optional mailer information printed in or above the address or in the lower left corner of the envelope. The information in a keyline identifies the mailpiece and its presort level. Under some postage payment systems, the keyline is a required line that contains specific information about the mailpiece.

 

Known Office of Publication —The business office of a Periodicals publication that is in the city where the original entry for Periodicals mailing privileges is authorized.