Buying email lists is evil. Don't be evil.
Few things are as antithetical to good inbound marketing as purchasing a list of strangers' email addresses and blasting them with your latest campaign. You may get a short-term win, but emailing to a purchased list can be detrimental in the long run.
Beyond that, it's bad practice in general and causes frustration for the recipients, who haven't opted in to hear from you.
There are also two significant business risks associated with emailing to a purchased list:
1. It will damage your sender score
A company's sender score, which is tracked by Return Path, rates the reputation of every outgoing mail server IP address on a scale of 0-100. A company's sender score is determined by an algorithm that takes into account the ratio of undeliverable emails and spam reports for a company's sends.
Purchased lists are naturally higher in hard bounces and spam reports, and they can wreak havoc on your sender score. If your sender score drops, it severely limits your ability to have your future emails—even good, non-spammy ones—end up in recipients' inboxes.
That is what one bad email list can do to your sender score.
2. It could get you blacklisted
In addition to harming your sender score, purchased lists can contain spam traps or defunct email addresses that may land you on an email blacklist. B2B companies in particular need to be careful, because many corporate domains will use spam reporting services such as spamcop to identify and completely block emails from blacklisted senders.
Grow your opt-in list via inbound marketing
Inbound marketing is a strategy that focuses on building useful, interesting content to attract subscribers and prospective customers. The basic idea is this: Provide value, make it relevant, and the subscribers will come. The whole point of subscribing to something is because you're interested in it enough to want to be clued in to all future editions.