Is it legal to put a letter in your neighbor's mailbox?

Answer 1

Existing residential mailbox laws state that only authorized letter carriers may insert mail into a residential mailbox. A penalty will be imposed for anyone who is not a letter carrier and is inserting mail in the residential mailbox. It is a federal offense for tampering with the mail and a fine or possibly jail time can be the punishment for the offense. Generally, resident mailboxes are for mail use only.

Answer 2

Not unless it was, perhaps, mis-delivered to your box instead, and you are doing your neighbor a favor by doing so. US Postal Regulations prohibit the placing of anything into a mailbox EXCEPT those items sent through, and delivered by, the US Postal Serivce. An exception to this would be, if the "mailbox" being referred to is actually a mail SLOT cut into the door or wall through which deliveries are made directly into the interior of a business or dwelling.

Answer 3

If a person writes a letter or a note to their neighbor and places it into their mailbox without placing postage on it, this is definitely illegal.

If they are writing a letter to a third party and properly stamp the letter, technically they can place the outgoing letter into any U.S. Mailbox. Most people are not crass enough to do this, however.

It is also illegal to deliver improperly delivered mail to the correct person's mailbox. It should be marked "Not at this address" and placed back in your own mailbox. Any other use constitutes mail tampering.