Abstract: This invention involves a method of automatically converting a random address file into a file with address entries in bulk mail order by package and sack groups, including postal endorsements used in a unique manner which indicates by a mere glance where mailpiece package groups separate, as well as eliminating the need for "D", "3", etc. stickers. It also produces a mailpiece count report which facilitates mailing statement preparation and postage calculation, and a mail sack label report which shows what must appear on each mail sack label needed for the mailing. It also permits the assembling of a kit which, when used by an inexperienced person with mailpieces, permits the easy preparation of a complete bulk mailing meeting postal verification standards.