Adapted from information provided by the U.S. Postal Service

• Type of mail: Foreign, Priority, Special Delivery
• Restrictive endorsements: Confidential, Personal, To Be Opened by Addressee Only
  
• Visual distractions: Fragile, Rush, Handle With Care
  
• Excessive postage (usually postage stamps)
  
• Fictitious or no return address
  
• Poorly typed or handwritten addresses
  
• Incorrect titles
  
• Titles but no names
  
• Misspellings of common words
  
• Oily stains or discolorations
  
• Excessive or uneven weight distribution
  
• Excessive binding material: masking, electric or strapping tape; string; twine
  
• Rigid, lopsided or uneven envelope
  
• Protruding wires, screws or other metal parts
  
• Postmarked from area different from return address