I think purchasing mailing lists is a poor investment. You’d make better use of your resources if you joined a couple of professional associations related to your website product or service. Members of an organization can usually get access to each others’ information and that information will be accurate, current and up-to-date.
I am a writer. I do purchase the Writer’s Market, which lists every agent, publisher, magazine, book, literary reviewer and writing-related resource in the world.
I still have to phone and find out the name of the current magazine editor, because these people change jobs frequently.
I am now building my list with QUALIFIED leads. The person or organization has to be someone who would be likely to use my services or who might work with others who would use my services. I will put names of people I meet on my list if they are participating in activities that show they have a common interest.
But I will not purchase a mailing list – even if the source is honest, much of the information is outdated by the time it’s printed up.