A comment from a list provider on a previous post inspired me to write this post because I want to warn you all.
Companies that advertise that they sell email lists "for as low as 60$" should never be trusted. Where did they obtain these email addresses? Did they scrape them off a bunch of websites or did they use other shady tactics like that? By purchasing a list and sending a campaign to that list, you'll be labeled as a spammer instantly. So stay away from them. Don't. Ever. Purchase. Lists. Period.
Please note that I am not saying that renting email lists is a bad idea. List rental can work. But you should always ask the list rental company how they got the email addresses, how they obtained the subscriber's permission (ask them to show you examples) and how often the list is emailed. The last thing you want is that your company/brand is labeled as a spammer for sending emails to people that didn't ask for them.
Also, make sure that it's the list rental company that sends out the emails. If they give you the list so you can send the emails from your system, run away as fast as you can. Seriously. If they are serious about their business they would never just give you the list. So if they do, I'm guessing they do it because they know they will get loads of spam complaints and bounces and they don't want to risk their own sender reputation.
Ask them to do a trial on a random subset of their list to see if you'll actually get a return for your money. List rental is not cheap and there are not a lot of good email lists out there to rent.
Last but not least, if you really think that renting an email list rather than building your own email list is a good practice, think again. The only reason why I would ever recommend someone to go out and rent email lists is when they want to get started with email marketing and they need to build their base from scratch. In that case, list rental could help you get started if you use it only to promote your own list.
Renting email lists should never be a long-term tactic. It's just not cost-effective enough.
I'm sure there are people out there that disagree with me. They are probably in the list rental business themselves :-) But, if you are not in the list rental business: feel free to share your experiences (good or bad) in the comments!