Whether it is illegal to park in front of or near a mailbox is a municipal issue – each local government has its own regulations, so you will need to check in your specific area. However, parking in front of a mailbox may be a violation of the United States Postal Service rules, specifically chapter D041 of the Domestic Mail Manual. In addition to the specific criteria that curbside mailboxes must meet, chapter D041 also mandates that mail recipients must allow a clear approach to their mailboxes or the USPS can withdraw mail service.
Curbside Mailbox Rules
The USPS has rules about curbside mailboxes including that manufactured boxes must meet agency specifications, while homemade boxes require prior USPS approval. Chapter 508 of the USPS Domestic Mail Manual mandates the location of all curbside mailboxes, specifying that the mail carrier must be able to reach a curbside mailbox without leaving her vehicle.