Top 10 Email Deliverability Terms You Need to Know

Posted by Mary Sohn on

Holy Niche Subject, Batman.

Email Deliverability is an incredibly specialized field. And with that comes a bucket of jargon and acronyms that can be hard to navigate. Here are the top terms I find myself explaining to email marketers. For a comprehensive list, download The Ultimate Email Deliverability Glossary.

  1. Blacklist: I find myself having to explain how a blacklist is different from being blocked. Blacklists are lists of IP addresses that have been reported and listed as “known” sources of spam. There are public and private blacklists. Public blacklists are published and made available to the public – many times as a free service, sometimes for a fee. There are hundreds of well-known public blacklists.
  2. Block: Different from blacklists, blocks are mailbox provider specific. This is a refusal by a mailbox provider or mail server not to accept an email message for delivery. Many mailbox providers block email from IP addresses or domains that have been reported to send spam or viruses or have content that violates email policy or spam filters.
  3. Cloudmark: A spam filter company that uses a network of users as a feedback mechanism to identify and block spam. As a result, Cloudmark filtering can look like impact from a block / blacklist because you’ll see delivery issues across mailbox providers that use Cloudmark for their spam filtering intelligence. Their Global Threat Network is fed by various means but most notably through their desktop spam filter and through ‘This is Spam” buttons that mailbox providers contribute through their Cloudmark Authority product.
  4. DomainKeys Identified Mail (DKIM): DKIM lets an organization take responsibility for a message while it is in transit. The organization is a handler of the message, either as its originator or as an intermediary. Their reputation is the basis for evaluating whether to trust the message for delivery. Technically, DKIM provides a method for validating a domain name identity that is associated with a message through cryptographic authentication.
  5. Inbox Placement Rate: Many senders confuse “delivery rate” with “inbox placement rate”. But this is where Return Path data shines and supplements your ESP data. Inbox placement rate is the rate of emails that were delivered to the inbox, versus the junk folder. Calculated as: (Number of Emails Delivered to the Inbox) / (Total Number of Emails Sent).
  6. List-Unsubscribe: The List-Unsubscribe header is text you can include in the header portion of your messages (note: this is not the email header in your email design, but your email “envelope”), allowing recipients to see an unsubscribe button they can click if they would like to automatically stop future messages. List-Unsubscribe is currently being used by iOS 10, Gmail, Windows Live and Cloudmark.
  7. Pristine Spam Traps: Email addresses created solely to capture spammers (sometimes referred to as honey pots). These email addresses were never owned by a real person, do not subscribe to email programs and of course will not make purchases. Many spam trap operators will post (seed) pristine traps across the internet on various participating websites. They are usually hidden in the background code of webpages and are acquired by a spambot scraping email addresses. If you’re hitting pristine traps this typically indicates you have a bad data partner or your signup process is allowing bogus emails into your list.
  8. Recycled Spam Traps: Email addresses that were once used by a real person. These email addresses are abandoned email accounts that are recycled by mailbox providers as spam traps. Before turning an abandoned email address into a spam trap, mailbox providers will return unknown user error codes for a year. Once mailbox providers reactivate (recycle) the abandoned email address, mail is once again allowed to be received by the email address. If you’re hitting a high number of recycled spam traps this typically indicates your data hygiene process is not working or your signup process may benefit from using “confirmed opt-in (COI)” aka “double opt-in (DOI)” to have new subscribers confirm that their address is still active. Here’s a great article from Litmus on the benefits of single opt-in (SOI) vs. DOI.
  9. Sender Policy Framework (SPF): A protocol used to eliminate email forgeries. A line of code called an SPF record is placed in a sender’s DNS information. The incoming mail server can verify a sender by reading the SPF record before allowing a message through.
  10. Sender Reputation Data (SRD): Used by Microsoft Live Hotmail and MSN Hotmail, SRD is a collection of non-biased responses from feedback loop participants over time. Along with other sources of reputation data such as the Junk Email Reporting Program (JMRP), the Windows Live Sender Reputation Data helps to train and improve the way Microsoft’s SmartScreen technology properly classifies messages based on email content and sender reputation.

Looking for more? Here are other helpful guides to help you!


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About Mary Sohn

Mary brings years of advertising experience to email and views deliverability data from a marketer's perspective. In her spare time, you'll find Mary eating through Canada's best diners, drive-ins, and dives (without the justification of a reality TV show). Follow Mary on Twitter @juenology for a haphazard glimpse into her life as a hungry-for-food email specialist.

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