I have used a number of different list services in the past, and I have found The Refinery as one of the better ones because they perform an initial validation prior to sending us the list. In your list parameters, you can insist on only titles that include Owner, Founder, and Partner, along with all other SIC/NAICS Codes, Region, etc. We then put the list through another validation process as an added email check. As mentioned above, telephone numbers can be tricky, and we have found that the numbers are generally the main office line.

I've added a few options here to check out:
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