Enclosures
Correspondence
Mail of any kind, for transport by the USPS, should be enclosed in an appropriate envelope or parcel and sealed. The types of enclosures determine the mailing classification.
Non-Machinable Enclosure
Before you design your mail piece, please contact the mail center at 7-8817 or the U. S. Post office, Mail piece Design at email address MDA@USPS.gov for more information.
Window Envelope Enclosures
Enclosures that are designed so that the address appears in a window folded to prevent movement of the address from window view. If the addressed enclosure does not properly fit the window, use an envelope without a window.