There are anti-spammers and ISPs out there who create fresh new email addresses, and post them on websites as "bait." They create these "spam traps" to capture spam-bots, who bounce around the Internet and "scrape" email addresses from websites.
This is why you never, ever buy those fishy email lists of "30 million opt-ins." You never know if there’s a spam trap on the
list (actually, you can pretty much count on them being on the list).
Here’s a nice article from ReturnPath with tips for keeping spam trap addresses off your list:
Some of their tips include:
- Use the double opt-in method (this is built into MailChimp’s list
management feature, by the way).
- Always remove email addresses that hard bounce. If you keep
sending messages to bad email addresses, ISPs assume you’re a bot
(MailChimp automatically removes hard bounces from your lists).
They also mention a different kind of method that’s kind of like
quarantining new emails to be sent from one specific IP address for a little while (read through all the "cohort" stuff). If your quarantine
IP address gets blacklisted, you dump those new addresses, because the list is "tainted." It’s an interesting tactic. It’s probably worthwhile if you’re a marketer who purchases lists on a regular basis (and ReturnPath happens to sell ECOA services). Guess you’d also need a good amount of IP addresses to spare too. I’d be a little worried about getting my entire range of IPs blacklisted, but these days few anti-spammers go that far. The blacklists that do block huge IP ranges generally aren’t being used by major ISPs anymore anyways.
At MailChimp, we’ve actually got a vaguely similar "quarantine" process, to help with our deliverability. Without going into too much detail, all "new" customers are kept within a certain range of IP addresses. As they send more email and become more and more trusted, they’re moved up the range to a set of IPs with other low-complaint, long-time customers. The idea is that if you’ve been with us for 5 years, you’re a lot less risky than someone who just signed up with us yesterday. Your campaigns should be sent from a different set of very stable IPs. Then we’ve got a range of IPs for users with double-opt-in lists in place. These are the least risky, and have the fewest complaint and deliverability issues. Just a little something we do behind the scenes to keep your campaigns running smoothly.