Yes you can, but no you shouldn’t. Like any get rich quick scheme, getting your hands on 20,000 new email recipients is never going to be as effective as organically growing your own customer base over time.
People on these lists aren’t familiar with you or your business, and might unsubscribe after a single email. They never consented to being emailed by you, and this could get you into some hot water if you annoy the wrong people.
Most importantly, most email marketing software won’t allow you to import a list of purchased contacts, so you might be wasting money. Just be patient and grow your own garden – don’t steal someone else’s overnight.