A newspaper tube must never block the visibility of a mailbox flag from the mail carrier. The mouth of the tube must never project further than the front of an adjacent mailbox. A tube must never touch a mailbox, block it from being seen clearly by on-coming traffic, or interfere with a mailbox's use in any way. A mailbox is considered federal property and can be used only by the U.S. Postal Service. The post is not considered federal property.