Pardot has written some great stuff on blacklists that I’ve linked before. Here’s the followup.
“First we’ll cover private blacklists, such as McAfee, Hotmail, and blacklists run by prospect IT teams on corporate email servers. These blacklists generally tend to be based on email content and email volume. However, since these blacklists are privately owned and operated, we cannot easily determine what specific element of an email necessarily caused the listing. In cases of private blacklisting, it’s a good idea to double check…”
Read more at How Do I End Up on a Blacklist? (Part 2) – Pardot.