Direct mail means printed material delivered or distributed by United States mail or other delivery service to a mass audience or to addressees on a mailing list provided by the purchaser or at the direction of the purchaser when the cost of the items are not billed directly to the recipients. Direct mail includes tangible personal property supplied directly or indirectly by the purchaser to the direct mail seller for inclusion in the package containing the printed material. Direct mail does not include multiple items of printed material delivered to a single address.