List Profit Boost Co-Registration Services
List Profit Boost Co-Registration Services involves a cooperative marketing effort between those catering to the same (or similar) niche market, where they promote each other’s offers to their subscribers. (“Email List Explosion”)
You can approach competing email marketers and offer them a joint venture opportunity, however until your list is a bit established, it is unlikely that you will be able to find many marketers who would be interested.