Separate all international mail from domestic mail. Separate all Canada and Mexico mail from the rest of the international mail.
Face all letter size envelopes in the same direction. Make sure none are upside down. When mailing letter size envelopes, flaps must be sealed, tucked in, or nested (overlapped).
Try not to overstuff letter-size envelopes. If this is not possible, you must seal the envelopes with tape before they are sent to Campus Mail to be processed.
All envelopes larger than a #10 size letter envelope must be sealed before being sent to Campus Mail.
Keep the top right corner of each mailing piece clear of all markings. This is where the postmark will appear.
USPS Mail Preparation
Bulk Mail Preparation