What market are you trying to attract? Is this the same as your current market? Does the market that you are trying to attract definitely exist?

Is the data opt-in? Does the provider adhere to DMA (Direct Marketing Association) guidelines?

How often has it been updated?

How was it collected? This is particularly important because different collection methods can have a bearing on the responsiveness of the list. Don’t accept vague answers.

Is the data generic or personal? (eg sales@ or joe.bloggs@)?

How regularly has it been sent to?

What kind of campaigns have been sent to the list? And what were responses like?