Publication 685 - Publication for Streamlined Mail Acceptance for Letters and Flats - Contents 6-2 Participation Criteria Participation in the Seamless Acceptance process is limited to mailings and mailers ..." /> Publication 685 - Publication for Streamlined Mail Acceptance for Letters and Flats - Contents 6-2 Participation Criteria Participation in the Seamless Acceptance process is limited to mailings and mailers ..." />