About Blacklists

You may occasionally see a bounce that has been recorded for an email you sent, and the reason for the bounce refers to a blacklist. Bounces are a normal part of sending email, and blacklists are a normal part of the way that email works. ClickDimensions believes in transparency, providing our customers with complete visibility into their delivery rates. Many email marketing systems will only tell you that some percentage of your emails bounced, but they may not show you all the reasons why. But every email marketing system in the world is subject to bounces caused by blacklists. Our goal at ClickDimensions is to provide you with the best overall delivery rates possible and to minimize bounces wherever possible.

What is a blacklist?

In an attempt to prevent unsolicited email (spam) from clogging people’s inboxes, many email services use a variety of tools to determine if an email is legitimate and desired by the intended recipient. One of the tools they use is an RBL, or remote blacklist. An RBL is a list of known or suspected IP addresses that are considered to be sources of spam. There are hundreds, if not thousands, of RBLs in the world. Some of them are maintained by large companies, and some are open source projects run by volunteers. (You could even start your own blacklist by publishing a list of IP addresses on a website and permitting email administrators to reference your list when checking the legitimacy of an email!)

How do blacklists work?

Blacklists, or RBLs, are a great tool that we all benefit from because they help us avoid having to wade through a bunch of spam and junk email. However, blacklists are not perfect. Some blacklists use manual reporting mechanisms where participants report suspected IP addresses to the blacklist. If enough people report the IP address, the blacklist may add it to their list of known or suspected sources of spam. Other blacklists uses algorithms to monitor and measure email that flows through the systems they monitor, ranking the volume, frequency, and content of the email messages and tracing the messages back to the source.

Regardless of the method of compiling a blacklist, mistakes are sometimes made and legitimate sources of email can be added to the list. In turn, the email service providers and spam filtering applications that reference a given blacklist may begin blocking email based on faulty information. (Of course, sometimes, the IP address really is a source of unsolicited email if it has been compromised by a spammer or if one person using a shared IP address for email decides to send a lot of junk.)

What can Email providers do about blacklists?

Due to the imperfect nature of blacklists, many blacklist providers offer a way for an email administrator to request “de-listing” – in other words, to ask the company maintaining the blacklist to reconsider, remove the IP from the list, or to provide additional information about how it got listed. Each blacklist provider has their own mechanism for handling these requests. And some blacklist providers have no mechanism to handle correction requests. Sometimes the process of de-listing an IP address is automatic when a de-listing request is received, sometimes the listing expires automatically, and sometimes the blacklist provider requires several rounds of discussion and proof before removing a blacklisted IP address.

ClickDimensions, like all companies that provide email marketing, has a deliverability team that works around the clock, monitoring the major blacklists around the world and working with the blacklist providers to keep our IP addresses off of their lists. By the time you see a bounce reported in your CRM due to a blacklist, chances are that our deliverability team has already begun working with the blacklist provider to request de-listing. In most cases, your marketing email is not affected by a blacklisting, but occasionally a small percentage of your overall email might be impacted by a blacklist. In these situations, you can rest assured knowing our deliverability team is working with the blacklist provider, or if you have a question or concern about a blocked email due to a blacklist, you can talk with our support team about it to find out more.

What Else can Cause Email to be rejected?

Blacklists are one method that email providers and mail servers might use to evaluate the legitimacy of an email, but there are other methods used as well. Some large corporations maintain their own internal blacklists based on their users interactions with emails or on other filtering mechanisms. Additionally, your recipients may use their email application, such as Outlook, to “block” future emails from you or your domain by moving your messages to their junk folder. Some antivirus applications will also scan a recipient’s inbox for suspicious email and occasionally mistake a legitimate email for a phishing attempt. (This can happen on the recipient’s computer, or on their corporate network.) In short, email delivery brings many factors into play, some of which you can help to control (for example, by sending timely, relevant email only to those who have given you permission to email them), some of which are in our control, and others which are beyond the control of the sending parties.

About Matt

Senior Director, Pre-Sales Consulting at ClickDimensions
Microsoft Dynamics CRM MVP
Author, The Microsoft Dynamics CRM 2011 Administration Bible