The USPS considers a mailpiece “nonmailable” if it cannot be accepted for processing even in non-automation areas, such as mailpieces not meeting minimum sizes or overweight mailpieces.

Items may be considered nonmailable based on different conditions, including:

  • Violating minimum / maximum size or weight, or shape restrictions.
  • Illegible address.
  • Prohibited material.

If presented for mailing at a local Post Office™, nonmailable items are refused and not placed into the mail system.

What Happens if a Nonmailable Item is Mailed Anyways?

Sometimes a nonmailable item may be mailed anyway (such as dropped in a Collection Box® receptacle). Generally, nonmailable pieces are returned to the sender immediately as soon as the reason for nonmailability is discovered.

There may be rare cases where a nonmailable item is not directly returned to the sender, based on:

  • Hazard of sending through the mail.
  • Nonmailability is due to a legal violation.
  • Packaging does not allow return or provide sufficient address to return.

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