Placing a note directly in your neighbor’s mailbox without sending it through the United States Postal Service (USPS) is technically illegal under United States law. According to Title 18, Section 1725 of the United States Code, it’s unlawful to deposit any mailable matter such as letters, postcards, or packages into a mailbox without proper postage. This law is enforced to ensure the security of the mail system and to prevent the unauthorized use of mailboxes.

For those looking to communicate with a neighbor, here are some legal alternatives…

1. Hand Delivery – Personally hand the note to your neighbor or leave it at their door.
2. Use a Door Hanger – Place your note in a door hanger on their doorknob.
3. Send it Via USPS – If you want to ensure privacy and formality, you can mail your note, even if it’s just going next door. This requires a stamp but ensures that you’re following the law.
4. Digital Communication – Consider using email, social media, or texting if you have your neighbor’s contact information and they’re open to digital communication.

Using any of these alternatives respects the legal restrictions and maintains the privacy and security of your neighbor’s mailbox.