How often is the list updated and/or cleaned (a "cleaned" list is one that has been processed by the U.S. Postal Service to flag recent changes of address and remove old non-deliverable addresses)? How frequently do people on the list make purchases, and how much do they spend?
ADDRESS ON SCHEDULE - Establish a reputation for addressing on time as promised. If you accept orders and fail to fulfil them on schedule, brokers become aware of this and find they can not conscientiously suggest your list to potential users. If, for some reason, you foresee a delay, ...