FAQ Can MAILERS+4 "Walk Sequence certify" my mailing list? Walk Sequenced mail gets the best discount.   It is used to saturate a neigborhood.   MAILERS+4 cannot Walk Sequence certify a list. It can Presort a list that has valid Walk Sequence codes. The List Services department can supply you with a list that is Walk Sequence certified. For more information on Walk Sequence mailing lists visit: www.mailerssoftware.com/listocc.html.