MediaBuyerPlanner: More than 550 ecommerce companies allow other marketers to place promos into outgoing packages, and the practice can be phenomenally successful.

In fact, using retailers from the likes of Amazon to Lillian Vernon, this tactic can result in 0.35 percent buyer conversion rates at a very low CPM - about a third of the price of a postal mail program - according to a new report from MarketingSherpa. The cost of participating in an outgoing package program can run as much as 30 to 40 percent less than the cost of renting names.

Companies interested in starting a package insert program of their own can make as much as a 60 percent margin on it.

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