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Email Marketing Glossary

50+ must-know terms to help you master email marketing


Above the Fold

The part of an email or web page that is visible without scrolling. It is generally more desirable placement because of its visibility.

Another word for permission. The recipient of your email has been clearly and fully notified of the collection and use of his email address and has consented prior to such collection and use. Affirmative consent is not only a best practice; it is required by all reputable email marketing services.


Also known as Application Programming Interface, an API is a programming tool to enable separate software programs to communicate with each other or work harmoniously within an operating system. Good examples are Java and Microsoft DirectX, a bundle of APIs that enable game programming and video on PCs.

Auto Responder

A program or a script that automatically sends a response when someone sends a message to its address. The most common uses of auto responders are for subscribe and unsubscribe confirmations, welcome emails and customer-support questions.



Lists of IP addresses designated as unauthorized senders by an Internet Service Provider, corporation, email server or user. Blacklisted IPs are usually spammers who send unsolicited commercial email or who are known to carry malware. Blacklists are either used or compiled by spam filters to block specific IP addresses.


Blocking occurs when an email is rejected from an inbox, often as a result of filters put in place by a user or Internet Service Provider.

Bounced Email

An email that is returned to the server that sent it. A bounced email is usually classified as either a “hard bounce,” which indicates a permanent failure due to a non-existent address or a blocking condition by the receiver, or a “soft bounce,” indicating that there is a temporary failure due to a full mailbox or an unavailable server.


Calls to Action

Often referred to as a CTA, this term refers to words included in images or text that encourage a prospect to take a specific action. For example, “Click here to see a product tour” or “Add this product to your wish list.”


A coordinated set of individual email marketing messages delivered at intervals and with an overall objective in mind.


Federal anti-spam legislation passed in 2003 that requires the following in each email: a legitimate header, a valid “From” address, a straightforward “Subject” line, an unsubscribe/opt-out link and/or instructions and a physical address. It also requires that all unsubscribes are processed within ten days of receipt. The Act is enforced and the first spammer convicted was a wardriver from Marina Del Rey, California. In July 2007, he was sentenced to three years of probation, six months of home detention and issued a $10,000 fine.


When a prospect takes an action and clicks on a link. To determine the click-through rate, divide the number of responses by the number of emails sent (multiply this by 100 to express the result as a percentage).

Click-to-Open Rate

To determine the click-to-open rate, divide the number of responses by the number of emails opened (multiply this by 100 to express the result as a percentage).

Confirmed Opt-In

A Confirmed Opt-In (also referred to as Double Opt-In) is a two-step process that allows a user to join your mailing list. The user must initially sign up, and then respond to a follow-up email prior to receiving any further email.


The substance of a web page, email, newsletter or any created work. Content communicates your message with copy, images, video, etc. It is your most important marketing element.

Conversion Rate

The number or percentage of recipients who respond to your call-to-action in a given email marketing campaign or promotion. This is the measure of your email campaign’s success. You may measure conversion in sales, phone calls, appointments, etc.


Double Opt-In

This is the preferred method of obtaining permission from your subscribers. The prospect signs up for email contact via a form, check box, sign up box, etc. The second step comes when the recipient responds to a verification email affirming that they wish to receive future emails. This is a safe way to build email lists and build subscribers’ trust in your campaign. See Confirmed Opt-In.


Email Blocking

Email blocking typically refers to blocking by ISPs. Emails that are blocked are not processed through the ISP and are prevented from reaching their addressed destination. ISPs actively block email coming from suspected spammers.

Email Deliverability

Email deliverability refers to the ability to deliver emails directly to a subscriber's inbox. As ESPs crack down on suspected spammers and unwanted emails, email deliverability is a major focus for all marketers.


Feedback Loop

The process by which the email client (ISP) of the receiver forwards complaints of emails marked as spam by recipients for removal by the sender. Usually treated by senders as an unsubscribe request. See Spam Complaint.


Hard / Soft Bounce

Emails that are undeliverable are called bounces. A “hard bounce” indicates a permanent failure due to a non-existent address or a blocking condition by the receiver. A “soft bounce” indicates that there is a temporary failure due to a full mailbox or an unavailable server.

Visible at the top of an email, it tells the recipient where the email has come from. Most headers will show the To and From lines, which identify the sender and recipient, and the subject line, which is meant to state the email’s purpose. Recipients often make the decision to open, trash or flag the message as spam depending on these attributes. An appealing header that accurately prepares the recipient for what the email contains is the surest way to gain a user’s trust.

House List

A permission-based list that you built yourself. Use it to market, cross sell and up-sell, and to establish a relationship with customers over time. Your house list is one of your most valuable assets.


HTML stands for HyperText Markup Language. Used by most web pages, it is the programming that translates coded formats into the images that you see. It serves numerous purposes, embedding videos and images and scripts and structuring a page’s content. To encode text inside emails or web pages, designers use HTML elements called tags. These tags are enclosed inside brackets. For instance,

<h1>is the start tag for a large header font. At the end of the header is placed an end tag, which includes a forward slash</h1>.


Landing Page

This term has many definitions but one essential purpose: it is the first page that appears when a prospect clicks on a link. Often it is the first page a visitor to your site will see: where they will “land” after clicking a search engine result or advertisement.


Mailing List

A group of email addresses (with or without additional information such as the subscribers’ names) to which specific mailings are sent.



“Opened” messages include HTML emails that have been viewed in a preview pane or fully opened in the email client, as long as images have been enabled. Opens are generally tracked by inserting a small clear image in an HTML message. When a message is opened and images are enabled, the image calls the server and the message is then counted as an open. Text messages cannot be tracked as opened because they cannot include images.

Open Rate

The total number of emails opened divided by the total number of emails delivered (multiply this number by 100 to express the result as a percentage).

Opt In

Also known as "subscribe." The action a person takes when he or she actively and explicitly requests, by email or other means, to receive email communications.

Opt Out

Also known as "unsubscribe." The action a person takes when he or she chooses not to receive email communications. It requires a web-based mechanism by which people can ask to be removed reliably from an email list. This request must be honored within ten days, as mandated by the CAN-SPAM Act.


Permission-Based Email

Email sent to recipients who have opted-in or subscribed to receive email communications from a particular company, website or individual. Permission is an absolute prerequisite for legitimate and profitable email marketing.


The practice of writing an email to make the recipient feel that it is more personal and was sent with him or her in mind. This might include using the recipient’s name in the salutation or subject line, referring to previous purchases or correspondence or offering recommendations based on previous buying patterns.


Criminal fraud by attempting to acquire personal information such as usernames, passwords, credit cards, etc. via email or bogus links. Often this takes place on false sites claiming to be legitimate versions of trusted ones. A prevailing method of identity theft.


The quality or condition of being free from unsanctioned intrusion. Communications need to reassure the prospect through clear, accessible and enforced assurances so he or she can feel comfortable about providing personal information and transacting business.



The end user who requested the email from the sender, usually identified by the email address in the ‘To’ line.

Rental List

Also referred to as an "acquisition list." A list of prospects or a targeted group of recipients who have opted-in to receive information about certain subjects. Using permission-based rental lists, marketers can send email messages to audiences targeted by interest category, profession, demographic information and more.


The estimation to which a sender is held by the community or the public as sending “good” or “bad” email. Many factors are used to determine a sender’s reputation, though spam complaints are the main metric considered.



Dividing your email list based on interest categories, purchasing behavior, demographics and more for the purpose of targeting specific email campaigns to the audiences most likely to respond to your message or offer. Your list segmentation and targeting efforts pay off with higher open and click-through rates.


The person or organization responsible for transmitting the email, usually identified by the email address in the ‘From’ line.


Unwanted email usually sent without the recipient’s permission.

Spam Complaint

The receipt of a complaint from a recipient who has identified the message as spam.


A technique used by spammers to dupe recipients into opening and replying to unauthorized emails. The sender alters the From address to trick a recipient into giving personal information to a trusted source. The mayhem is two fold in that it exposes the user to identity theft and damages the reputation of the address the spoofer is counterfeiting. Spoofing often goes hand in hand with phishing scams.

Subject Line

The title of an email. This is the first (and hopefully not last) element of the communication recipients will see when they access their email. It has to grab attention and be credible or the email will not be opened.


Subscribe means to sign up - to give permission to someone to send you newsletters, email or other electronic information.



Selecting a portion of the mailing list with similar demographic values to send messages relevant to those demographics.


Collecting and evaluating the statistics (or metrics) that measure the effectiveness of an email or an email campaign.



Unsolicited Commercial Email (also referred to as spam). Commercial email sent without the recipient’s express permission.

Unique Click

A click from a single user. When unique clicks are measured, it is an aggregate number of how many times that URL was clicked by individual users. Duplicate clicks by a single user do not affect the total.


Simply put, this is the address of a web page on the world wide web. It is also known as the Uniform Resource Locator. More specifically, this is a global address of documents or resources on the internet. It is made up of two elements separated by a colon and two forward slashes. The first part of an address is called the protocol identifier, described below. The second part is the resource name: the IP address or domain name where the resource is located (e.g., The protocol identifier determines what protocol to use. For example, a protocol identifier may be in HTTP or FTP. HTTP (HyperText Transfer Protocol) defines how web servers and browsers respond to commands. When you enter a URL in your browser, the HTTP directs the web server to pull up the requested web page. FTP stands for File Transfer Protocol.


To cancel a service such as the delivery of an email newsletter or mailing list. In Benchmark, an unsubscriber is a person who has asked to be taken off your mailing list.



A grammatical property of verbs that indicates a relationship between the subject and the action expressed by the verb. “Birds build nests” is written in the active voice and emphasizes the subject: birds. “Nests are built by birds” is written in the passive voice and emphasizes the action - building nests. Active voice is far more persuasive in driving action.



Lists of contacts or IP addresses authorized to pass through a spam filter by the user. The senders in this case are not spammers and their email is pre-approved regardless of subject lines or content. The opposite of a blacklist.


The question at the forefront of every email recipient's mind when making a decision to open, read and then take action on your email (e.g., click a link, call for an appointment, visit an office or retail location).