It Harms Your Sending Reputation
People change their email addresses and providers regularly; purchased email lists are almost always out of date as the data is usually farmed months, and sometimes years, in advance. In addition to the old addresses, the lists might contain a large chunk of fake addresses too. These factors typically lead to extremely high bounce rates (a bounce is when an email returns because the address is invalid) and unsubscribes. The higher bounce rates and unsubscribes will raise a red flag and the reputation of the domain you're sending from (e.g. "@yourbusiness.com") will drop significantly. What this means is that the next time you go to send email, of any kind, the likelihood of being sent to spam increases.
It Yields Lower Response Rates
In most instances, list marketers will tell you up front that purchased lists have lower response rates. This is because when you send to someone who is not yet familiar with your brand and products, or has yet to have any interaction with your business via email, the emails you're sending will more than likely drop right into their spam inbox where they'll never see your message. It's called "blind sending" and almost always results in lower response rates. In fact, once you're dubbed "spam", the chances of you ever breaking through to their inbox disappears almost entirely.
It's Sometimes Illegal
Depending on where you live in the world, sending to massive email lists you've purchased can have legal repercussions. This is especially the case when you are doing email marketing with the use of commercial mailing lists that were bought and resold to you illegally... without you knowing it. Privacy is a big deal today, the last thing you want to do is get caught up in a storm of complaints as a result of leaked personal information that was resold to thousands of third-parties (e.g. Target's recent data breach). There are a number of things that you are legally required to do when sending email and services such as MailChimp and CampaignMonitor will be the first to not only tell you that purchased lists are a no-go, but block you from using them entirely. This is for your protection!
It's Not Personal
The names and email addresses you receive when purchasing an email list are nothing more than static data. These people have no relationship with your brand, know nothing about your products, and are certainly not expecting an advertisement from you. They don't know you. Any salesperson will tell you that a warm lead is better than a cold one. The best way to generate warm leads is by slowly and carefully establishing a relationship with each contact on a personal level. You can do this by acquiring data on your subscribers correctly (e.g. forms on your website, Facebook promotions, etc.), organizing it in a way that suits your email marketing goals, and leveraging the information to build out highly targeted and personalized campaigns.
Think about it like this, a campaign sent to people that have purchased your product before with suggestions for similar products they may be interested in will yield significantly better results than an email you send to somebody about something. That is why it is advisable to carefully craft your messages to suit the needs and requirements of the people that you will be sending them out to.
A quality email marketing database is very valuable and can take years to build. However, the results from a smaller quantity of email addresses that you've molded and marketed carefully and effectively is far greater than a massive list of email addresses you've purchased and blasted with an advertisement.
Looking to start sending better email? Stop by our Email Marketing services page to view our cost-effective packages that won't require a contract and are designed with growing your brand in mind.