FAQ What payment options and rate types does MAILERS+4 support? There are 3 payment options to choose from. Meter – Indicates that you will use a postage meter to pay for your mailing. Imprint – Indicates that you will use a permit imprint to pay for your mailing Stamp – Indicates that you will use pre-cancelled stamps to pay for your mailing. You can enter the stamp value in the field provided on the Postage Statement information screen. MAILERS+4 supports the following rate types.. Profit: Applies to regular mail outside the nonprofit category Nonprofit: The processing of Nonprofit Mail is exactly like Standard Mail (A). the difference is in the rates that are charged. USPS Nonprofit rate authorization is required prior to mailing. Classroom: A special periodical rate available to educational, scientific, or religious publications that are used for scholastic or religious instruction. Science of Agriculture: A special periodical rate for agrarian publications (70% of the subscribers must be rural residents).