The CAN-SPAM Act makes certain types of e-mail address collection illegal and requires permission from your e-mail list subscribers before you send certain types of content. (The CAN-SPAM Act uses the term affirmative consent instead of permission.)
Potentially illegal e-mail address collection methods aren’t always easy to spot, so the best practice is to make sure that you have explicit permission from everyone on your list to send them e-mail. Here are some best practices for steering clear of potentially permissionless e-mail addresses:
Never purchase an e-mail list from a company that allows you to keep the e-mail addresses as a data file. E-mail addresses kept in a data file are easily bought and sold, and e-mail addresses with explicit permission are too valuable to sell.
Never collect e-mail addresses from websites and other online directories. This isn’t a good practice because you don’t have affirmative consent (or permission) from the owner.
Don’t use an e-mail address collection service. The exception is a service that collects confirmed permission from every subscriber that it obtains.
Don’t borrow an e-mail list from another business and send e-mail to that business’s e-mail list. Those subscribers didn’t explicitly opt in to receive your e-mails.
Don’t rent an e-mail list unless you’re certain that the list rental company’s practices are legally compliant. Most rental companies don’t have permission-based lists.