We allow enclosures if they don’t:

• Damage postal equipment
• Damage other mail
• Cause injury to postal employees

For the best processing, make sure the mail item doesn’t vary in thickness more than 2 mm across its length and width. We accept enclosures that vary in thickness if the thickness of the thinnest enclosure is no less than half the thickness of the thickest enclosure. Non-paper can tear through envelopes or wrappers during machine processing. To prevent this, give special attention to both the strength of wrappings and how well the enclosures fit in them.