Glossary of Email Marketing Terms

18 Terms Every Email Marketer Needs to Know

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No need to consult a book for these email marketing terms. StockUnlimited

Find to-the-point definitions for essential email marketing words, phrases and acronyms in this glossary.

Talk and Understand Email Marketing with the Conviction of Knowledge

Wish your conversations with the head of email marketing were shorter—with you asking her less often "what does that word mean?" (and "what does that mean for us?" more often)?

Care to confuse, both, and impress the director of marketing with intricate knowledge of arcane uses for certain acronyms in email delivery?

Want to gloss over gloss over blog posts and listen to podcasts without pausing (at 2x the speed) assured you know and understand the key terms of email marketing?

The definitions are here—and easy to look up.

A/B Split

In an A/B Split, a mailing list is divided randomly into two equal segments, each of which receives a different message, or a message at a different time, for example. So, the influence of these variables can be tested, as all other things are as equal as possible between the two parts.


An email blacklist (also DNS blacklist) contains IP addresses that are blocked for sending spam.
Receiving email servers can check one or more blacklists and refuse to accept email from any IP address that appears on at least one of the blacklists. Senders can apply for their IP address to be removed, which should happen when certain criteria are fulfilled.

Sometimes, blacklist refers to an email user's list of blocked email addresses.

Call to Action

The call to action is the part of an email—frequently a button, image or text link—that asks the recipient to take the action the sender desires them to take (e.g. filling out a questionnaire, ordering a product or confirming their subscription).

Co-Registration (Co-Reg)

With co-registration or coreg, the sign-up process for one list includes the option to also sign up for another list from a third party. For example, the sign-up form for a web site's newsletter might offer a checkbox that lets users also sign up for a sponsor's emails at the same time.

Click-Through Rate (CTR)

The click-through rate measures how many recipients of an email did click on a link in that message. The click-through rate is computed by dividing the number of clicks by the number of emails sent.

Dedicated IP

A dedicated IP address is one that only one sender uses to deliver email. With shared IP addresses, it is always possible that others send unsolicited email from the same IP address, and it gets listed on a blacklist of known sources of spam. Your email will be blocked along with the actual offender's messages.

Double Opt-In

With double opt-in (also sometimes called "confirmed opt-in"), it is not enough for a potential subscriber to enter their email address on a site or possibly other form; he or she also needs to confirm both the email address as their own and their intent to subscribe. Usually, this is done by following a confirmation link in an email or by replying to such an email from the address that is to be subscribed.

ESP (Email Service Provider)

An ESP, short for Email Service Provider, offers email marketing services. Typically, an ESP lets its customers build, manage and filter lists, design and deliver email campaigns as well as track their success.

Email Address Harvesting

Email address harvesting is the usually unlawful process of gathering email addresses for deliver junk email to them. The addresses can be obtained by purchase, for example, or by having a robot scan pages on the web for email addresses.

Feedback Loop

A feedback loop notifies bulk email senders when users mark their message as spam. This happens for larger senders with an excellent reputation, so they can take action in these cases.

Hard Bounce

A hard bounce returns an email to the sender when the message could not be delivered because the user (or even the domain name) does not exist.

Honey Pot

A honey pot is a blank and unused email address that helps identify spam; since the address is not subscribed to any lists, any message sent to it in bulk must be unsolicited. Of course, honey pots also include the potential for abuse if the address ever becomes known as s spam trap.

Open Rate

The open rate measures how many recipients of a mass email did open the message. It is calculated by dividing the number of opens by the number of recipients. Opens are typically determined with a small image that is downloaded when the message is opened; this is also the limitation, as plain text emails do not include images, and many email services and programs will not download them automatically.


Personalization has a bulk email adapted for individual recipients. This can be as simple as using the recipient's name, but also involve changing the message depending on the recipient's purchase or click-through history.

Soft Bounce

With a soft bounce, an email message is returned to the sender as currently undeliverable. Common reasons include a full mailbox, an email that exceeds the size the server supports or a temporary block. Often, email servers will try again to deliver the message automatically after a delay.

Suppression List

A suppression list contains email addresses that are never sent messages from a sender. People can request to be put on the suppression list to prevent others from signing them up for mailing lists maliciously, for example.

Transactional Email

A transactional message is a message sent typically in response to a user action that is not (or at least not only) promotional but part of an interaction with the user.
Typical transactional emails include welcome and good-bye messages for a newsletter, shipping notifications, invoices, other confirmations or reminders.


whitelist is a list of senders whose emails are prevented from being treated as junk email. A whitelist can be specific to an email account and user, but also valid across all users of a web-based email service, for example.

(Updated August 2016)