Dictionary A to Z icon for email marketing terms

Email Marketing Terms: 150+ Definitions You Need to Know

If you're new to email marketing, it might seem like this practice has its own language. If you find yourself saying "That's Greek to me!" we've got a comprehensive list of email marketing terms you need to know.

Even if you're not a newbie, some of these email marketing terms may have flown under your radar. So, if you ever hear or read something that makes you go hmm, come back to this glossary to find an answer.

We've organized the definitions for these email marketing terms by categories. So, if you're looking to learn about a specific topic you can jump right to the terms you want to learn. Let's start beefing up your email marketing vocabulary skills!

Table of content

General email marketing terms 

Blast (batch-and-blast) 

An email sent to a large number of recipients, often the entire subscriber list or the entire contact list. In some cases, you could consider an email to a segment of a list to be an email blast, but it would have to be a large segment.

Call-to-action (CTA) 

The key step you want subscribers to take after reading all or part of your email, such as ‘click here’ and ‘buy now.’ When the user clicks on a call-to-action link, they’ll be taken to a landing page. The CTA often appears in the form of a button, but can also be a simple text link or a graphic. 


Any person listed in your email database. A contact may just consist of an email address or it may include a person’s name, other contact information like a phone number, and even past order history or account data. A contact is different from a subscriber who’s opted in to receive emails. Your contacts may include people who never provided consent to receive marketing emails or who have unsubscribed.  


The process of sending an email campaign to a predetermined email list or list segment. 

Email body 

The primary text and messaging of an email. When you open an email, you begin reading the email body, which may also include photos, graphics, animations, and links. The body begins after the greeting and ends before the email footer.

Email campaign 

A series of emails that serves a consistent marketing purpose or goal. This could be a sale of a product or service, an invitation to an event, a contest, etc. It usually has a similar call-to-action throughout, and often includes an end point or deadline. See three email campaign management challenges.

Email client 

The computer or phone program interface used by anyone who wants to send or receive email. An email client could be web-based, such as Yahoo or Gmail, or software-based, such as Microsoft Outlook, iOSMail, and Mozilla Thunderbird. See Inbox Service Provider. Find out more about email client stereotypes.

Friendly from 

A sender name that features a person’s name, rather than the name of a company or an email address. It comes across as more personal than receiving email from a company, but can also cause confusion if subscribers aren’t familiar with the name being used.

From address 

This is the email address of record that is sending the email. It may be different than the actual person who is really sending the email. For example, admin@yourcompany.com could be the from address, but a variety of people within a company could be able to send emails using that address. The from address does not have to be the same as the reply-to address. 


Gmail App for Non Google Accounts is email terminology for when someone uses the Gmail app for an email address that is not a Gmail account. Get more info on developing emails for Gmail.

Inbox Service Provider (ISP) 

A web-based platform that powers the ability for users to send and receive emails. This is where your email address ‘lives’. Most inbox service providers offer this service at no charge, but may include ads or offer additional paid services. Others, like Rackspace, offer premium email service for a fee. (AKA mailbox provider, MBP)


All the customers, subscribers, and contacts for whom you have email addresses. 

Mailbox provider (MBP) (See Inbox Service Provider) 

Another term for an inbox service provider. 


An email that goes out on a consistent basis that provides updates, news, tips, other helpful information, and ways to take action in response to the content of the email newsletter. Email newsletters are distinct from email campaigns in that they don’t have just one purpose for being sent.

No-reply address 

An email address that can send emails but not receive them. 

Preheader text (preview text) 

This text usually appears next to or below the subject line. In most mailbox providers, the subject is bolded and the preheader is not. Preheader text does not show up in the email body, unless the sender doesn’t write any preview text. In that case, the preview text usually defaults to the first text appearing in the email. See ten examples of effective preheaders.

Preview pane 

Some email clients, particularly Microsoft Outlook, enable the email recipient to preview the email without opening it, using the preview pane. This lets them see a bit more of the email than just the subject line and preheader text, and they can then decide if they want to open it to view the full message. 

Promotional email 

An email sent on behalf of a company or organization for marketing purposes, rather than from a person or for transactional purposes like documenting a purchase or providing a shipping update. Promotional emails are typically sent in bulk, to entire email lists or to segments of them. Contacts who opt in to receive promotional emails become “subscribers.”


Anyone with an email address who receives an email from someone else. 

Reply-to address 

The address to which any replies to a message are sent. In some situations, the from address may differ from the reply-to address. This means that the email address that has sent a particular email is not the same as the one recipients will reply to. A company might do this if they expect a large number of replies and don’t want the from address to get overloaded with emails. 


The person, company, or organization that’s sending an email to another individual or to email addresses on their list. 

Sender name 

This text appears next to the subject line in a mailbox provider. It indicates the name of the person or company that has sent the email. It can be adjusted by the sender no matter who is actually sending the email. 

Subject line 

The text that informs the recipient what the email is about. Subject lines appear in email clients, usually next to or below the sender name. The subject line is separate from the email body. See some good spring subject line and summer subject line examples.


Anyone on an email contact list who has opted in to receive emails from that sender, which may be a company, a blog, or another type of organization. Subscribers can opt out by unsubscribing, at which point they should receive no more emails from that sender.  Find out how to avoid annoying your subscribers.

Transactional email 

An automated email that relates to the completion of a particular task, usually triggered by an action taken by an individual recipient. Typical transactional emails include receipts, shipping updates, password resets, and signup confirmations. Improve your transactional email design.


One branch of mailbox providers that can only be accessed through a web browser. The most popular webmail clients are Yahoo and Gmail. 

Email marketing technology terms

Content Delivery Network (CDN) 

A geographically-distributed array of servers that speed up delivery time of emails and other stored content due to being closer in proximity to each user. CDNs also increase security and redundancy to protect data in the event of hardware failure at one location. 

Customer Data Platform (CDP) 

A software platform that unifies all the data about each customer from all other platforms and touchpoints to build a single customer profile. CDPs enable increased levels of personalization and segmentation the more a customer interacts with the owning organization.

Customer Relationship Management (CRM) 

A software platform that organizes customer transactions and engagement data to make it accessible and useful for a company’s marketing and communication efforts. CRMs enable organizations to manage and enhance customer interactions as the customer relationship develops over time.

Email editor 

Within an email service provider’s platform, the email editor is where you build the actual email by adding text, images, links, and graphics, or inserting code for custom-developed emails. Various editors can let you use code, templates, drag and drop blocks, and other tools depending on the software’s capabilities. See our list of top email development tools.

Email Service Provider (ESP) 

A company that provides a software platform – typically on a monthly or annual subscription – allowing the user to collect and manage an email list, build and send emails to that list, monitor data such as opens and clicks, create segments, and more. 

Marketing Automation Platform (MAP) 

A service provider that allows companies to create email marketing automations such as welcome series, abandoned cart emails, a lapsed customer series, and any other trigger-based email automations. See 35 of the best marketing automation platforms

Email design terms 


Email design elements that enable people with physical or mental impairments to easily and fully engage with an email. See email accessibility best practices and learn how to conduct an accessibility audit. 

Animated GIF 

An image format composed of a short sequence of still images that gives the impression of motion. Animated GIFs tend to last for just a few seconds, at most. See how popular brands use GIFs in email marketing.


A way to display more images and content in a single location within an email. A carousel rotates through a series of images, often featuring one at a time while still revealing parts of the other images. Here’s how to write code for an interactive carousel

Dark mode 

A screen setting that alters the appearance of an email to be more pleasant on the eyes in a dark or dimly lit setting. Instead of dark text on white backgrounds, the background becomes darker and the text lighter, and other design elements are altered for a similar effect. Learn more about dark mode emails.

Dynamic content 

Email content that changes depending on the characteristics and previous actions of each subscriber or other data that’s pulled in real-time. Using fields to fill in personalized information for each recipient, dynamic content enables senders to include information such as names, companies, previous purchases, accurate countdown timers, weather information, and any other data they may have for the contacts in that segment of their email list. See examples of dynamic content in email.

Fluid/Hybrid design 

A design approach that alters images and tables based on the size of the display, but doesn’t deliberately alter the text or layout. Fluid design tends to adapt well regardless of the device or the email client used, and differs from responsive design in the mechanics of how it adapts to different screen sizes.

Image blocking 

An email setting that prevents any images or graphics from displaying in the user’s inbox. Any images in an email that lands in an inbox using image blocking will display only the image’s alt text. 

Image validation 

The process of checking HTML image parameters to confirm that an image will display properly in the recipient’s email client. Learn how to perform image validation.

Image-only email 

An email with no text, only graphics. If a user has images disabled, they will only see the alt text in image-only email. 

Inbox display 

The elements of an email that show up in a recipient’s inbox before they open it. This usually includes the sender name, subject line, and pre-header text. Optimizing your inbox display increases your open rate.

Interactive email 

An email that includes features that respond to a subscriber’s actions within the email. This could include dropdowns, videos, or popups. 

Modular email design 

Emails that are built with content blocks that can be rearranged as needed. Blocks can include text, buttons, graphics, and various other elements. Get tips on creating an email design system with modules.

Plain text email 

An email format with no images, no HTML code elements, and no formatting such as bold and italics.

Responsive design 

An email designed to display in the best possible format depending on the device being used to view it. Responsive design adjusts to the screen size and functionality of each device. 


A pre-designed email structure that includes core design elements, headers, and footers, and that a sender can fill in with text, messaging, and design elements specific to their campaign and company. Templates speed up the email creation process and ensure consistent branding. See how to test your templates

Text-to-image ratio 

The ratio of text characters to image characters. Image characters are counted based on the HTML code that represents the image and is unaffected by the size of the image. A text-to-image ratio that was too low used to increase the risk of being flagged as spam, but this may not be as big of a risk today.

Web fonts 

Fonts that are uploaded from a server and are not pre-loaded onto a device or platform. Using web fonts increases your ability to be creative and stand out. But not all web fonts are supported in all email clients or devices, which is why font stacks with fallbacks must be incorporated alongside them. Learn how to use web fonts and font stacks.

WYSIWYG editor 

Any email editing platform that shows you how the email will look to your recipients, as you create the email. What you see in the email editor is what your contacts will see when they receive it, and you don’t need to know HTML to use it. Most email service providers employ WYSIWYG editors.

Email development terms 

Alt text 

Text that describes an image or other graphic and must be added to the code when you create an email. If an image doesn’t render for any reason, the alt text will appear in its place. Screen readers can read alt text so people with vision impairments can understand the nature of the image.

AMP emails 

Accelerated Mobile Page was an internet technology launched in 2015 meant to make websites work much faster on mobile devices. AMP emails enable senders to embed dynamic content, media, forms the recipient can fill out, and other more interactive elements within their emails. See if AMP emails convert better than HTML email campaigns.


Describes an email element like a button or a background that is written with code instead of relying on images, with the goal of ensuring it displays correctly regardless of how the email is viewed by the subscriber. Learn how to make bulletproof buttons and backgrounds.


Specifies the space between the wall of a table’s cell and the content within that cell. More cellpadding means more white space.


All the major parts of an email, including the header, footer, subject, pre-header, from name, call to action, body content, images, and share buttons. 

Conditional code 

Specially formatted code that allows an email to display differently in different email clients. Conditional code is most often utilized so emails will render correctly in Microsoft Outlook.

Email framework 

A sort of shortcut to creating responsive design emails using ‘markup’ language. Frameworks allow you to quickly create emails using a variety of customized email templates, and without having to get into the HTML. 

Email preview 

A step in the email testing process where you examine how your email will display in various devices, email clients, and mailbox providers. 

Email weight 

The size of an email, in kilobytes or megabytes. The HTML weight usually gets measured in kb, but the overall email in MB. 


What email recipients see when your primary content fails to display due to some incompatibility with the email client. This could mean they see a different font or the alt text for an image. Get some fallbacks for interactive emails.

Font stack 

A list of fonts, in order of preference, that lets an email client know which fonts your email should be displayed in. If the preferred font is incompatible for some reason, the remaining fallback fonts will take its place, again in order of preference until a compatible one is found. Get everything you need to know about email fonts.

Ghost table 

An element of hybrid email design that forces Microsoft Outlook to display columns side by side or as otherwise intended, because Outlook often doesn’t stack columns very well. They’re called ghost tables because they’re a form of conditional code, invisible to email clients other than Outlook. See how to fix Outlook alignment issues with ghost tables.


Code at the top of an email that is unseen by the recipient, the email header authenticates the message and helps prevent it from being categorized as spam.

Inline CSS 

Special code inserted within the HTML of an email to ensure the style functions as intended. This is related to embedded CSS and external stylesheets, but different email clients offer varying levels of support for each, with external sheets frequently disabled due to security risks.

Media query 

A special block of CSS code that lets you customize your media content for different devices and purposes. It’s an optional media element triggered by certain characteristics of the email client or device. Learn how to use media queries in HTML.

Minify (HTML/CSS) 

The procedure of reducing non-essential code elements without compromising functionality in an email. Minification speeds up load time and reduces email weight (file size). Learn how to minify HTML. 


Mailjet Markup Language is one of the most common email frameworks, used to simplify the use of customized templates without needing to use HTML. See email framework above. Learn how to use MJML to code responsive emails.

Progressive enhancement 

A method of building emails that begins with the most essential elements to ensure functionality, usability, and clarity, and then builds on those with increasing complexity, responsiveness, styles, and conditional code. It also includes appropriate fallbacks, so the email displays and functions across all email clients and devices. Learn more about progressive enhancement.

Pseudo element 

A specially inserted keyword within the HTML that allows you to uniquely style one element in an email different from the rest, such as a button, a paragraph, or a subheading. Learn how to use pseudo elements


The process of email clients interpreting and displaying your email. Your email may “render” differently for each subscriber based on thousands of possible combinations between their device, email client, and more.

Semantic HTML 

HTML code that clearly identifies the purpose of the code. For example, <div> doesn’t reveal what the code means, but <table> does. Therefore, <table> is semantic HTML.


Small blocks of code that can be reused across multiple emails for elements that appear frequently for that sender. This could include elements like bulletproof buttons, footers, and email signatures.

Table role 

An adjustment within the HTML code for tables allowing you to specify how the table will be read by a screen reader. For people with visual impairments, setting table role to “presentation” will help the screen reader clearly communicate what’s in the table, as opposed to a cascade of nonsense. 

Email marketing strategy terms

A/B test  

Sending two versions of the same email to randomized portions of the same list, where the emails differ in one or more details such as subject line, CTA text, an image, opening copy, etc. The version that gets better results will be sent to the remainder of the email list or used in future campaigns. See A/B test results on email length.

Abandoned cart email  

An automated email sent to any subscriber who places items in an online ‘shopping cart’ equivalent, but then doesn’t complete the purchase process. The abandoned cart email reminds them of their unpurchased items and motivates them to complete the purchase. Learn how cart abandonment emails maximize ROI. 


Any automated email or series of emails that goes out in response to a particular action taken by the recipient, such as signing up for a newsletter, buying a product, or downloading a free resource.

Behavioral email 

Similar to a trigger email, a behavioral email is sent out based on actions taken by the recipient. For example, a customer who buys a particular product could receive an email offering deals for related accessories. 

Bounce rate  

The percentage of email sends that bounce – meaning they get returned as undeliverable and do not reach the intended email address – compared to the total number of emails sent to that list of subscribers. A 1% bounce rate means 1 out of 100 emails came back as undelivered. 

Click-to-open rate (CTOR)  

The percentage of emails that were clicked on compared to the number of emails that were opened. If 500 emails are opened, and 50 of those are clicked on by different recipients, that’s a 10% click-to-open-rate. A CTOR is more informative than a CTR as it relates to the effectiveness of the email content, because it focuses only on those subscribers who opened and saw the email. 

Clickthrough rate (CTR)  

The percentage of emails that get clicked on compared to the total number of emails sent. If 5000 emails get sent, and 50 of those get clicked on by different recipients, that’s a 1% clickthrough rate. 

Drip campaign  

An automated email campaign featuring a series of pre-timed emails that are sent over a period of days, weeks, or months after the recipient takes a particular action. A drip campaign is one type of an autoresponder.

Email strategy terms  

Email terminology related to email strategic planning. Campaign, autoresponder, welcome series, newsletter, and segmentation are some examples of email strategy terms.


Evidence of any type of response by recipients to an email sent to them. Engagement usually refers to actions like opening, clicking, sharing, responding, following, and converting. See metrics to measure engagement. 

List building  

Any marketing strategy with the goal of adding more subscribers to an email list.

List churn  

The number of people unsubscribing from your email list in a given period of time. List churn is one reason why list building is so important. Otherwise, the email list shrinks over time. 

List fatigue  

The situation – perceived or real – when an email list seems to lose its responsiveness or interest in what the sender is communicating. 

List growth  

The number of new subscribers and contacts added to your email list in a given period of time. 

Mail merge  

A word processing tool that allows you to insert personal information such as names, titles, and addresses into documents that are being mass-produced, so each recipient gets a letter that is personalized to them.

Merge tag 

The email equivalent of a mail merge.

Nurture track/nurture sequence  

A marketing campaign that goes out after a new lead has been acquired, with the goal of eventually turning them into a paying customer. Nurture sequences can involve email as well as other forms of media. Learn how to nurture leads with email. 

Onboarding emails  

When a new customer is acquired, they receive a sequence of automated onboarding emails that introduce them to the company, provide helpful and inspiring information, and offer perks, deals, and other opportunities to further engage. The same term applies to when a company hires a new employee.

Open rate  

The percentage of emails that are opened compared to the total number of emails sent. Find out how to increase your open rates.


Any effort to send emails that use each recipient’s unique data and information to more effectively communicate with them.

Progressive profiling  

The process of collecting subscriber data in small bits at a time, as opposed to all at once. Get tips on asking for subscriber data. 

Re-engagement campaign  

An email campaign specifically designed for subscribers and customers who have not engaged with any emails for a particular amount of time, such as six months, or a year. 

Read, Skim, Glance/Delete  

Engagement metrics that seek to show greater insights into subscriber behavior than just opens and clicks. Each can be set to different lengths of time, but read must be longer than skim, and glance/delete means they opened it and deleted it right away. See examples of email engagement analytics.


Breaking an email list into smaller groups defined by particular attributes such as engagement, buying history, demographics, or product preferences. See how to segment your email list to boost ROI.

Tracking pixel  

A piece of software code that tracks how a user engages with an email, website, or other online asset.

Trigger email  

An automated email that gets sent out after a recipient takes a particular action, such as clicking on a link. Trigger emails sometimes go out immediately, but may also get sent several days after the triggering event. 

Unique opens  

The number of distinct subscribers who open an email. Unique opens are meant to differentiate from total opens so that contacts who open the same email more than once aren’t over-counted.

Unsubscribe rate  

The percentage of contacts who unsubscribe after receiving a particular email compared to the total number of emails sent. See the top ten reasons people unsubscribe from email lists. 

Welcome series 

An automated email series that is sent to a new subscriber and attempts to deepen their new connection with the company using a variety of strategies. See examples and tips on creating an email welcome series.

Email authentication terms 

Authentication protocols 

Any of the various tools that work to verify that an email really is from who it appears to be from. Authentication verifies the sender’s legitimacy, and enables mailbox providers to filter out spam, forged and spoofed emails. Learn about the four main email authentication tools


An authentication protocol that inserts the logo of the brand that is sending the emails in the inbox display, along with the sender name, subject line, and preheader text. Learn how to implement BIMI.


An authentication protocol that adds the equivalent of a ‘digital signature’ or watermark to the email header, to verify the authenticity of the sender’s domain. The “signature” does not show up for subscribers by default. Learn more about DKIM.


An authentication protocol that functions more like a policy – DMARC tells the receiving email server what to do when an email fails either the SPF or the DKIM protocols. See why you need a good DMARC policy.

MX Record 

The ‘mail exchange’ record specifies which email server an email should be sent to when it’s received. 


When emails are identified as spam or otherwise untrustworthy, they can be filtered into quarantine. This may mean the spam or junk folder, or they may be placed in isolation elsewhere without the recipient ever seeing them. 


An authentication protocol that specifies which IP addresses are authorized to send emails from a particular domain. Learn more about SPF.


Impersonating a legitimate email sender in an attempt to collect personal data from recipients, transmit viruses, or perform other nefarious actions. Email spoofs often link to fake websites made to look like the company they’re impersonating. How to stop email spoofing from hurting your brand.

Email deliverability terms 

Acceptance rate (deliverability rate) 

The percentage of emails that are delivered to the intended location in the recipient’s inbox compared to the total number of emails sent. Acceptance rate informs the sender of how many of their emails are being quarantined or rejected, and is distinct from delivery rate in that an email could be delivered, but then filtered into spam or promotional folders. To learn more, read 7 causes of deliverability problems. 


A list of external email domains that you’ve given permission to email your domain. If emails intended for you are being identified as spam, but you know the sender is legitimate, you can add them to an allowlist to ensure that they’re sent through. 

Bayesian filter 

An analytical tool that attempts to identify spam emails by looking for certain characteristics and types of content in the header of the actual email, and comparing those to common spam traits.


A list of email domains that have been banned from sending emails to your email domain. Any emails sent from blocked domains will be rejected or quarantined. Learn how to avoid or remove your domain from a blocklist.


A U.S. anti-spam law that regulates email marketing and sending behavior in an attempt to protect consumers from malicious, abusive, and exploitative email content. CAN-SPAM is the reason companies must include an unsubscribe option and postal address in every email and must clearly label emails as promotional. What to know about CAN-SPAM compliance.

Dedicated IP 

An IP address that is assigned to a specific domain and not shared by any others. 

Delivery rate 

The percentage of emails that do not bounce, but are delivered to the intended recipients, compared to the total number of emails sent. Delivery rate will always be higher than deliverability (or acceptance rate), because delivery rate does not account for emails that are filtered into spam or other quarantine options. 

Email harvesting 

Using various software techniques to unethically collect email addresses that appear in the code or on the page of websites. 

Email validation 

Confirming that an email address is correct. email validation looks for spelling errors, such as ‘con’ instead of ‘com,’ and other techniques to weed out incorrect email addresses and thus improve delivery and deliverability rates. See why email validation is so important. 

Email verification 

Very similar to email validation, verification also includes the attempt to confirm that an email is not fake, and that a real person is using that account. 


When a spam filter or authentication protocol incorrectly identifies an email as spam or suspicious, when it is, in fact, legitimate. 

Hard bounce 

An email that is returned as undeliverable because the email address is no longer active or never existed at all. Hard bounces should be removed from an email list. 


An inactive email address that is used in such a way as to attract spammers. No honeypot email address will ever opt into an email list. Thus, any emails received by the honeypot confirm the sender as a spammer. 

Inbox placement rate 

The true ‘deliverability rate’ in a sense, this is the percentage of emails that actually arrive in the main inbox of each recipient compared to the total number of emails sent. Inbox placement rate excludes all other folders and methods of email quarantine.

IP warming 

The practice of demonstrating the legitimacy of a new IP address by strategically increasing email volumes over time. IP warming is important because, when a brand new domain suddenly sends out huge volumes of email, it usually gets labeled as a spammer.

List hygiene 

The practice of regularly removing inactive, incorrect, invalid, bounced, and otherwise bad emails from an email list. See best practices for list hygiene. 

Opt in/opt out 

The decision of an email subscriber to join an email list, or to be removed from it by unsubscribing.

Seed list 

A small list of email addresses – often in-house – that you can send an email to in order to confirm that it functions correctly on various platforms and devices before sending it out to your main email list.

Sender reputation 

A score assigned to any email-sending organization that determines the likelihood of internet service providers delivering their emails. This is based on contact engagement, quality of content, and other factors.

Shared IP 

An IP address that is shared by multiple domains, a common arrangement for businesses that have their content hosted on a shared server. 

Soft bounce 

When an email bounces for what may be a temporary reason, such as a full mailbox, a vacation auto-reply, or a server issue. Soft bounces must be monitored on a case-by-case basis for a time before that email is removed from the email list.

Spam trap 

An abandoned, misspelled, fabricated, or recycled email address used to catch spammers by making them believe it’s a real email address. These are similar to honeypots. Real businesses can get caught by spam traps if they don’t practice good email list hygiene, which can damage their sender reputation.


Unwanted and unsolicited emails sent – usually in bulk – by individuals or organizations that are often not legitimate businesses. 


An anti-spam software service that identifies spam and the source of it, and uses that data to downgrade the sender reputation so future emails from that sender are marked as spam by mailbox providers. Find out what your SpamAssassin score means.

Suppression list 

A list of email contacts that you don’t want to send emails to because you’ve identified them as harmful to your sender reputation. The suppression list prevents these emails from somehow ending up on your active email list again.

Email privacy and compliance terms 

Apple Mail Privacy Protection (AMPP) 

A service from Apple Mail that prevents email senders from seeing subscribers’ IP addresses. This keeps them from knowing subscriber locations and other information, then using that to send more targeted marketing messages. It also thwarts efforts for senders to accurately measure open rates. How to find out if your subscribers use AMPP.


The California Consumer Privacy Act. A California-based law that requires businesses to disclose information they possess on any consumer who asks for it. They must also reveal any other parties they’ve shared that consumer’s information with. The CCPA applies to companies above a certain size that serve California residents. What to know about CCPA compliance and email marketing.

Consent (express and implied) 

When an individual agrees to receive email marketing communications from a business organization. This usually happens as part of the opt-in process. Express consent occurs when someone knowingly and willingly subscribes to email communication. Implied consent occurs when someone takes an action such as placing an order, contacting customer service, or requesting a password reset. Only transactional (non-commercial) emails are allowed with implied consent.

Double opt-in 

After filling out an opt-in form, an automated email is sent to a new subscriber and requires them to confirm by clicking a link that they really do want to receive email marketing from an organization. Double opt-in ensures a cleaner email list. 

DPO (Data Privacy Officer) 

Required of some organizations by the EU, a data privacy officer ensures that a company’s email communications and practices are in compliance with all the major applicable privacy laws.


The General Data Protection Regulation. A sweeping data privacy law from the EU that requires certain practices and limitations for any organizations that send email and use customer data in various ways. What to know about GDPR compliance and email marketing.


A compliance policy for the payment card industry that places requirements on how organizations must protect consumer credit card and payment information.

Personally identifiable information (PII) 

Any online information that reveals the identity of the individual it belongs to. This is the data that privacy laws and regulations are meant to protect.

Preference center 

A function of a website that allows subscribers to manage their email communications with an organization. They may be able to specify how many emails they want to receive as well as the type of content included. 

Privacy policy 

A webpage that details how an organization handles the data of its web visitors. 

Unsolicited Commercial Email (UCE) 

The polite way to describe spam. This term’s more likely to be used when the sender is a reputable organization sending legitimate messages, but to non-subscribers.

Unsubscribe link 

A link that usually appears near the bottom of an email that gives the recipient the option to stop receiving emails from that organization. See the top ten reasons people unsubscribe from email lists.

Technical email terms 


An application programming interface that lets other software applications integrate with the email functionality of the email service provider, so the user can send emails with other online tools. 

Dedicated IP 

An IP address that is assigned to a specific sending domain and not shared by any others.


Typically the first line of code in an email, DocType tells the email client which type of HTML is being used so the email renders correctly.


Internet Message Access Protocol allows emails to be accessed and read from any computer or mobile device, because the email remains stored on the server until you open it or attempt to download attachments. IMAP is distinct from POP. 

Mail delivery agent (MDA) 

Software that accepts emails sent to it from a mail submission agent via the mail transfer agent. The MDA then sends that email to the mail user agent so the recipient can read it. 

Mail submission agent (MSA)

Software that takes any emails sent by a mail user agent and submits them to the mail transfer agent using SMTP, which then delivers them to the mail delivery agent.

Mail transfer agent (MTA) 

Software that sends and receives emails using SMTP. The mail transfer agent takes emails from the MSA and transfers them to the MDA.

Mail user agent (MUA) 

Another term for an email client, which enables the recipient to read an email. The MUA receives emails from the mail delivery agent, or sends them to the mail submission agent.

MIME (Multi-Purpose Internet Mail Extensions) 

An upgrade to SMTP that enables things like audio, video, and graphics to be transferred in emails, in addition to just text. MIME also increases the security of the email transfer process over what SMTP can provide. See tips for integrating video into your email marketing.


As opposed to IMAP, POP works by downloading all your emails to your specific device, and then deleting them from the email server. This means you can only open your emails on the same computer or device that you first used to download them. Certain internet service providers that also offer email service use POP.


A special email address representing the email server, which receives and sends communications when problems arise in an email account, often a breach of security or a deliverability failure. 

Shared IP 

An IP address that is shared by multiple domains, a common arrangement for businesses that have their content hosted on a shared server. 


Simple Message Transfer Protocol is how your email client sends emails to your email server, and from there to the recipient’s server. SMTP is distinct from IMAP and POP in that those determine how the email arrives in the recipient’s inbox so they can read it.


Limiting the number of emails sent from a server over a given period of time. The goal of throttling is to avoid looking like a spammer, who would typically send out huge numbers of emails all at once. Throttling sends out smaller numbers of emails in batches.

Other unknowns in email marketing

Not knowing what different email marketing terms mean is scary enough. What's downright horrifying is not knowing how your carefully crafted campaigns will look in different inboxes.

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