How does Mailchimp know if I’ve purchased a list?

If you buy a list of email addresses and try to import them into Mailchimp, your account will be suspended.

Just how big is the email spam problem?

According to data collected from 400 million email accounts between 2012 and 2014 by the Messaging, Malware and Mobile Anti-Abuse Working Group, “abusive email remained fairly consistent, ranging from about 87.1% to 90.2%” (per month over the 30 months of the study). Yes you read that correctly; the vast majority of email messages are spam, malicious or similar.

This illustrates the enormous amount of unwanted emails that are sent and highlights why the significant email marketing services are making such efforts to reduce the number of spam and abusive emails that their clients send. Mailchimp call their ‘abuse prevention initiative’ Omnivore however, whether it has a name or not, all the good email EDM services use a spam prevention system where a content-filtering tool that can help increase email delivery rates before you actually send your email is used (as Constant Contact notes).

In August 2015, the IronPort Antispam System processed a total of 8,305,819 email messages. 6,647,772 of these messages were identified as Spam by our filters, of which 28,223 was Suspected Spam; and 511,332 as Marketing – 80% Spam. The University of Texas

How Mailchimp knows if a subscriber hasn’t agreed to receive communication

One thing that Mailchimp (and other email marketing services such as Constant Contact, Aweber and Mad Mimi) do is run imported subscriber email addresses through a database of known honeypot email addresses. If a honeypot email address appears in a list then it’s clear that the list contains email addresses that have been fraudulently attained.

Some of the more prolific spammers rely on bots that crawl millions of Web sites and “scrape” addresses from pages … additionally, there are a handful of open-air markets where lists of emails are sold by the millions. If you buy in bulk, you can expect to pay about a penny per 1,000 addresses. Brian Krebs

A honeypot email address is usually an email address that is placed on a webpage; this email address is machine generated and is monitored. Scraper bots (a ‘bot’ that exists purely to harvest email addresses from websites) are used widely to collect and record email addresses. These lists of email addresses may then be sold to people buying lists of email addresses (for marketing or malicious purposes).

Keep in mind that the scraped honeypot email addresses are purely placed on a webpage to be scraped by bots so that a sender to one of the honeypot email addresses can be identified as a spammer (i.e. the sender is clearly sending to an email address that hasn’t given permission to receive the communication as the honeypot email address isn’t a real person so couldn’t have given permission).

The honeypot email addresses are shared with Mailchimp and others when they are created. It is therefore really simple for Mailchimp to compare imported email addresses with those in a honeypot database. If you’re importing a list with honeypot email addresses there is a good chance you’ve purchased a list of subscribers.

Why does Mailchimp care if I send to a fake email address?

Mailchimp is a United States based company. It has a legal responsibility to avoid sending spam messages per the CAN-SPAM act. Furthermore, as email messages sent through Mailchimp are sent from the Mailchimp IP addresses and domains, if a significant proportion of emails sent are marked as spam then spam filters will start to mark all Mailchimp sent emails as spam. This of course would be devastating to their business.

Please, just don’t buy lists of subscribers. For one you’re supporting malicious activity, secondly you are going to get very low response rates from your email marketing and third, you’ll get your Mailchimp, Aweber, Constant contact etc. account suspended.