In offering a premium email delivery platform to our customers we carefully monitor our IPs for listings on significant blacklists. The Marketo Privacy team maintains relationships with the major blacklists to better assist our customers in resolving these issues. When we find that one of our customers was responsible for a blacklisting we contact that customer and request some actions be taken to remediate the issue.

In many cases we find that sending an email to a spamtrap address caused the blacklisting.  Spamtraps are email addresses that have either never been used or have not been used for a long time and are now owned by anti-spam organizations. They are considered by these organizations as a sign of poorly maintained or inappropriately acquired addresses. Based on this assessment they conclude that the marketer is sending spam and consequently blacklist the sender.

To prevent future blacklistings you'll need to review your recent activity to remove the spamtrap from your mailing. Finding the spam trap address can be difficult; they are closely guarded secrets of the blacklisting organizations and they do not share these addresses.

We describe several strategies below. The best approach for you depends on the make-up of your database and the amount of behavioral history in your Marketo system. The goal is to isolate potential spamtrap addresses and remove them. The group of addresses you select should be broad enough to capture those potentially bad addresses but small enough not to suppress a huge portion of your database.

Blacklists are not all the same - some provide Marketo with more information, some with less. If at all possible we will provide you with a date and a subject line to help you isolate potential traps.

        Step 1
        To narrow the list of potential traps you should consider the following: