• by Jess Nelson , September 23, 2016

Being blacklisted can have severe consequences for an email marketer -- leading to lower deliverability rates that can last as long as two weeks, according to a recent study by email and data solutions provider Return Path.

An email blacklist, also referred to as a DNS-based blackhole list, is a database of email senders who have sent too many emails considered to be spam. There are several different blacklists that track whether or not an IP is sending unwanted emails, but each has their own specific set of criteria.

If blacklisted, an IP address becomes “known” as a source of spam and as a direct consequence of the spammy behavior, the sender’s reputation and deliverability rates will drop. A blacklist does not have control over whether or not an email gets delivered, but email service providers rely on these lists as guidelines for their own protocol on email deliverability. 

In the report, Email Marketing For Retailers, Return Path compiled a list of recommended tactics to maximize the overall return of investment of email campaigns. The company looked at six different blacklists, including Spamhaus and SpamCop, to determine the average amount of time it takes to be removed from a blacklist.

The SpamCop Blocking List (SCBL) is a blacklist of IP addresses that have been reported by SpamCop users, but it is perhaps the easiest list to be removed from. A typical blacklisting only lasts for a day, and 86% of requests are removed from SpamCop within one day or less, according to Return Path. 

Other blacklists are not as forgiving, however, and require much more time and resources until removal can be done. A quarter of IPs blacklisted by Spamhaus will take more than a week to be removed from the list after a request, and nearly a third of those blacklisted on cbl.abuseat.o (CBL) will take more than a week to be removed from the blacklist.

In addition, 30% of email senders blacklisted by psbl.surriel.com (PSBL) will take a full two weeks to be removed from the list after a removal request.

The best way to avoid email blacklists is to maintain a healthy email list and high sender score. High spam complains are the most likely culprit of being blacklisted, so marketers need to ensure that their messages are wanted, relevant and timely.

Inaccurate email addresses, or bounce backs, can also damage an email sender score so it is also important for marketers to review their list acquisition tactics and sources to maintain an up-to-date database of email addresses.