There are many spammers engaging in email harvesting. The ISPs and domain holders want to identify them by setting up spam traps, also known as “honey pots.” The spam trap is an email address positioned on the ISP’s home page. That email address doesn’t belong to anyone, so when it is used by mailers, it becomes fatal for their reputation.
You can protect yourself from getting caught in the “honey pot.” One of the defensive methods is an application of double opt-in to verify email addresses. Another method requires sending double opt-in messages from a separate domain and IP address. Double opt-in also prevents from getting blacklisted.
To be more proactive against spam trap, you should use clean lists from ensured resources. You can buy or rent lists, but you have to make sure that they come from reputable sources.