|It is important to keep in mind U.S. Postal Service requirements when designing your envelopes.
- All mail .25 inches thick or less must be:
- Rectangular in shape,
- At least 3.25 inches high, and
- At least 5 inches long.
- A mail piece must be at least .007 (7 pt.) inches thick when it does not exceed 4.25 inches in height and 6 inches in length.
- A mail piece must be at least .009 (9 pt.) inches thick if it is either greater