Email Marketing Dictionary: A-Z Glossary of Key Terminology with Definitions

If you're new to email marketing, this email marketing dictionary (also called a "lexicon," "terminology guide," or "glossary") will help you understand the terms used in email campaigns.

The glossary includes everything from basic design terms like responsive layouts and ALT text to important delivery terms like SPF and DMARC.

There are now more than 300 definitions inside, grouped into groups such as Design, Legal/Compliance, Performance Metrics, and Security. It labels each word with its group, like "WYSIWYG" for "Design" or "BIMI" for "Branding." The definitions are written in simple language, with examples to help you understand.

This glossary is your quick guide to understanding the language of email marketing, whether you're trying to fix a problem with how Outlook renders emails, boost click-through rates, or just brush up on GDPR rules. You can use it to find words, look through groups, or send it to your team!

What This Email Glossary Includes

This resource provides a comprehensive list of terms related to email marketing, deliverability, design, and office jargon.

You'll find definitions for technical terms, design principles, legal requirements, performance metrics, and general email concepts. Each term is explained in simple language and includes examples to help illustrate its meaning.

Brief Overview of Categories

To make the glossary easier to navigate, the terms have been organized into several categories:

• Design: Terms related to the visual appearance and layout of emails.
• Deliverability: Terms concerning the ability of emails to reach recipients' inboxes.
• Engagement: Terms that describe how recipients interact with emails.
• Authentication: Terms related to verifying the sender's identity.
• Legal/Compliance: Terms related to laws and regulations governing email marketing.
• Technical: Terms referring to the technical aspects of email systems and technologies.
• General Email Terms: Common terms used in the context of email.
• List Management: Terms related to managing and maintaining email lists.
• Performance Metrics: Terms used to measure the success and effectiveness of email campaigns.
• Security/Privacy: Terms related to the security and privacy aspects of email.
• Branding: Terms related to establishing and maintaining a brand identity in emails.
• Workflow: Terms related to the processes involved in creating and sending emails.
• Content: Terms related to the text and other media within emails.
• Personalization: Terms related to tailoring email content to individual recipients.
• Marketing: Terms related to email as a marketing tool.
• Typography: Terms related to the style and appearance of text in emails.
• General Business Terms: Common terms used in the business context.

Each definition in the glossary will have its category noted in parentheses after the term, for example, "WYSIWYG (Design)". This categorization should help you quickly find terms related to a specific area of interest.

Complete Email Glossary

A

• A/B Split Test (Performance Metrics): Comparing two versions of something (like an email subject line or a website button) to see which one performs better.
• Above the Fold (Design): The part of an email visible without scrolling.
• Accessibility (Design): Making sure that emails and websites can be used by everyone, including people with disabilities.
• Adaptive Layout (Design): An email or website design that changes to fit different screen sizes.
• Allowlist (Whitelist) (Deliverability): A list of trusted senders.
• ALT Text (Alternative Text) (Design): A written description of an image that shows if the image doesn’t load.
• AMP (Accelerated Mobile Pages) for Email (Technical): Lets you add interactive elements to emails.
• AMPscript (Technical): A programming language used within the Salesforce Marketing Cloud.
• Analytics (Performance Metrics): The process of collecting and analyzing data to understand how people interact with your emails or website.
• Anchor Text (Design): The clickable text in a hyperlink.
• Animated GIF (Design): An image file that supports animation or moving pictures.
• Animation (Design): Moving elements like GIFs or videos in emails.
• API (Application Programming Interface) (Technical): A set of rules and tools that allows different software applications to communicate with each other.
• Approval (Workflow): The process of getting content (like an email) reviewed and approved before it's sent out.
• ARPANET (Technical): (Advanced Research Projects Agency Network) A precursor to the internet.
• Attachment (General Email Terms): A file that is sent along with an email.
• Attribution (Performance Metrics): Identifying the source of something, like where a website visitor came from.
• Authentication (Security/Privacy): Verifying the identity of someone or something.
• Authentication Protocols (Deliverability/Security): Methods to prove you’re a legitimate sender.
  • DKIM (DomainKeys Identified Mail) (Deliverability/Security): A digital "seal" that ensures your email wasn’t tampered with during delivery.
  • DMARC (Domain-based Message Authentication) (Deliverability/Security): A policy that tells email providers what to do if SPF or DKIM checks fail.
  • SPF (Sender Policy Framework) (Deliverability/Security): A "guest list" for your email domain.
• Autoresponder (General Email Terms): An automatic email that is sent out when someone takes a specific action.

B

• Background Image (Design): An image placed behind text/content in an email.
• Base64 (Technical): An encoding scheme used to represent binary data in an ASCII string format.
• Bayesian Filter (Technical/Security): A statistical technique used to identify spam emails.
• Bcc (Blind Carbon Copy) (General Email Terms): Sending an email to multiple recipients without showing their email addresses to each other.
• B2B (Business-to-Business) (General Business Terms): Companies that sell products or services to other businesses.
• B2C (Business-to-Consumer) (General Business Terms): Companies that sell products or services directly to individual consumers.
• B2B2C (Business-to-Business-to-Consumer) (General Business Terms): A business model where a company sells to another business, which in turn sells to consumers.
• B2C2B (Business-to-Consumer-to-Business) (General Business Terms): A business model where a consumer sells to another consumer, who then sells to a business.
• BIMI (Brand Indicators for Message Identification) (Branding/Deliverability): Lets your brand logo appear next to emails in the inbox.
• BITNET (Technical): (Because It's Time Network) An early academic computer network.
• Blacklist (Deliverability/Security): A "blocklist" of IPs/domains marked as spammers.
• Blast (General Email Terms): Sending the same email to a large group of people at once.
• Blocklist (Deliverability/Security): A list of email addresses or domains that you don't want to receive emails from.
• Body Copy (Content): The main text of your email.
• Bounce (Deliverability): When an email fails to reach the inbox.
  • Hard Bounce (Deliverability): Permanent failure (e.g., invalid email address).
  • Soft Bounce (Deliverability): Temporary issue (e.g., recipient’s inbox is full).
• Bounce Rate (Performance Metrics/Deliverability): The percentage of emails sent that could not be delivered to the recipient's inbox.
• Brand Guidelines (Branding): Rules for using your brand’s colors, fonts, and tone in emails.
• Bulk Folder (General Email Terms): The spam/junk folder.
• Bulk Mail (General Email Terms): Sending out a large number of emails at the same time.
• Bulletproof Button (Design): A CTA button that displays correctly even if images are blocked.
• Buyer Persona (Customer Persona) (Marketing): A semi-fictional representation of your ideal customer.

C

• Call-to-Action (CTA) (Design/Engagement): A button or link that tells readers what to do next.
• CAN-SPAM Act (Legal/Compliance): U.S. law regulating commercial email.
• Casl (Canada's Anti-Spam Legislation) (Legal/Compliance): Canadian legislation aimed at protecting consumers from spam.
• Cc (Carbon Copy) (General Email Terms): Sending an email to multiple recipients, with all recipient email addresses visible to each other.
• CDN (Content Delivery Network) (Technical): A network of servers that distributes web content to users based on their geographic location.
• CGI (Common Gateway Interface) (Technical): A standard way for web servers to pass requests to an application program.
• Closing (General Email Terms): A polite way to end an email.
• CMS (Content Management System) (Technical): A software application used to create and manage digital content.
• CNIL (Commission Nationale de l'Informatique et des Libertés) (Legal/Compliance): The French data protection authority.
• Cold IP (Deliverability): A new IP address with no sending history.
• Color Contrast (Design/Accessibility): The difference in brightness between text and its background.
• Column Layout (Design): Dividing email content into vertical sections.
• Complaint (Deliverability): When an email recipient marks an email as spam or junk.
• Complaint Rate (Performance Metrics/Deliverability): The % of people marking your email as spam.
• Consent (Legal/Compliance/List Management): Permission that is given to receive emails or have personal data collected.
• Content Filtering (Deliverability/Security): Spam filters scanning your email for red flags.
• Conversion Rate (CR Rate) (Performance Metrics): The percentage of people who complete a desired action.
• Copywriting (Content): The art of writing persuasive text for marketing or advertising.
• Cost Per Mile (CPM) (Performance Metrics): The cost an advertiser pays for one thousand views or impressions of an advertisement.
• CSS (Cascading Style Sheets) (Design/Technical): Code that styles email elements.
• CTR (Click-Through Rate) (Performance Metrics/Engagement): The percentage of people who clicked on a link.
• Customer Acquisition Cost (CAC) (Performance Metrics): The total cost of acquiring a new customer.
• Customer Lifetime Value (CLTV or LTV) (Performance Metrics): The total revenue a business expects to earn from a single customer over the entire duration of their relationship.

D

• Dark Mode (Design): A display setting that inverts colors.
• Data Protection (Legal/Compliance/Security): Laws and regulations designed to protect personal information.
• Data Protection Commission (DPC) (Legal/Compliance): The Irish data protection authority.
• Data Subject (Legal/Compliance/Security): An individual whose personal data is being processed.
• Dedicated IP (Deliverability): An internet protocol (IP) address that is used exclusively by one sender.
• Deliverability (Deliverability): Whether your email reaches the inbox (not spam).
• Delivery Rate (DR) (Performance Metrics/Deliverability): The percentage of emails that successfully reach the recipients' inboxes.
• Design System (Design): A set of standards, guidelines, and reusable components used to create a consistent look and feel.
• Dithering (Design): When email clients approximate colors not in their palette, causing a grainy look.
• DKIM (DomainKeys Identified Mail) (Deliverability/Security): A digital "seal" that ensures your email wasn’t tampered with during delivery.
• DMARC (Domain-based Message Authentication) (Deliverability/Security): A policy that tells email providers what to do if SPF or DKIM checks fail.
• DNS (Domain Name System) (Technical/Deliverability): The internet’s "phonebook" that connects domain names to IP addresses.
• DNS Server (Technical): A server that translates domain names into IP addresses.
• Doctype (Technical): An HTML declaration that specifies the document type.
• Dormant Users (List Management): Subscribers who have not engaged with your emails for a long period.
• Double Column Layout (Design): An email or website design that arranges content in two columns side-by-side.
• Double Opt-In (List Management/Deliverability): Subscribers confirm their signup via a confirmation email.
• DSAR Request (Data Subject Access Request) (Legal/Compliance/Security): A request made by an individual to access the personal data that an organization holds about them.
• Dynamic Content (Content/Personalization): Email or website content that changes based on the individual viewing it.

E

• Email Alias (General Email Terms): An alternative email address that forwards messages to your main email account.
• Email Appending (List Management): The process of adding email addresses to an existing database, often from third-party sources.
• Email Banner (Design): A visual at the top of an email, often used for branding or announcements.
• Email Client (Technical): The app or service used to open emails.
• Email Correspondence (General Email Terms): The exchange of messages via email.
• Email Customer Journey (Marketing): The path a customer takes through a series of emails.
• Email Etiquette (General Email Terms): The rules of polite and professional behavior when communicating via email.
• Email Header (Technical): The section at the top of an email that contains technical information about the message.
• Email List (List Management): A collection of email addresses that a sender has permission to email.
• Email Loop (Technical): A situation where emails are continuously sent back and forth between two or more email addresses.
• Email Mapping (Marketing): Planning the sequence and triggers of emails in a marketing automation campaign.
• Email Signature (General Email Terms): A block of text that is automatically added to the end of an email.
• Email Thread (General Email Terms): A group of emails that are part of the same conversation.
• Email Trail (General Email Terms): The history of an email conversation.
• Email Warmup (Deliverability): The process of gradually increasing the volume of emails sent from a new IP address or domain.
• Embeding (Technical): Including content like images or videos directly within the body of an email.
• Engagement (Performance Metrics): How recipients interact with your emails.
• Encrypted Email (Security/Privacy): Email that is protected using encryption techniques.
• Envelope (Technical): The technical information about an email that is used by mail servers to route the message.
• ESP (Email Service Provider) (Technical): Tools that send emails and track performance.
• Evergreen Spam Trap (Deliverability/Security): Old, abandoned email addresses used by ISPs to catch senders with poor list hygiene.
• Empty Space (Whitespace) (Design): Blank areas around text/images to reduce clutter.

F

• Favicon (Design/Branding): A tiny logo displayed in browser tabs.
• Federal Commissioner for Data Protection (BfDI) (Legal/Compliance): The German data protection authority.
• Feedback Loop (FBL) (Deliverability): Alerts you when someone marks your email as spam.
• Fixed Design (Design): An email or website design that has a set width.
• Fixed-Width Layout (Design): Designing emails to a specific pixel width.
• Fluid Layout (Design): A design that stretches or shrinks to fit screen sizes.
• Flow (Marketing): A series of automated emails triggered by specific actions or events.
• Fold (Design): See Above the Fold.
• Footer (Design): The bottom section of an email with unsubscribe links, address, and social icons.
• Forward (General Email Terms): To send an email you received to another person.
• From: Address (General Email Terms): The sender name/email recipients see.
• Funnel (Marketing): The stages a customer goes through from first becoming aware of a product or service to making a purchase.

G

• Garante per la protezione dei dati personali (Legal/Compliance): The Italian data protection authority.
• GDPR (General Data Protection Regulation) (Legal/Compliance/Security): A European Union law that regulates the processing of personal data and privacy.
• GIF (Design): A short, looping animation.
• Graymail (General Email Terms): Legitimate but low-interest emails.
• Greylisting (Deliverability/Security): Temporary email rejection to test if the sender is a real server.
• Greeting (General Email Terms): The salutation at the beginning of an email.
• Grid System (Design): A layout structure that aligns content into rows and columns.
• Gradient (Design): A smooth transition between colors.

H

• Hamburger Menu (Design): A collapsible menu used in mobile-friendly emails.
• Hard Bounce (Deliverability): An email that could not be delivered due to a permanent reason.
• Header (Design): The top section of an email with a logo, navigation, or headline.
• Hero Image (Design): A large banner image at the top of an email.
• Hex Code (Design/Technical): A 6-digit code representing colors.
• Honey Pot Trap (Deliverability/Security): A hidden email address planted on a website to catch spammers.
• Host (Technical): A server that stores and serves website files.
• Hot Lead (Marketing): A potential customer who is highly interested in a product or service.
• HTTPS (Technical/Security): Secure links.
• Hybrid Layout (Design): An email design that combines elements of both fixed and responsive layouts.

I

• Icon (Design): A small graphical symbol used to represent something.
• Ideal Customer Profile (ICP) (Marketing): A description of the perfect customer for your business.
• IMAP (Internet Message Access Protocol) (Technical): A protocol used to access email on a mail server.
• Image Blocking (Deliverability/Design): When email clients disable images by default.
• Inbound Marketing (Marketing): A marketing strategy focused on attracting customers through relevant and helpful content.
• Inbox Placement Rate (Performance Metrics/Deliverability): % of emails that land in the inbox (vs. spam).
• Ink Trap (Design): Tiny gaps in fonts to prevent smudging in print.
• Integration (Technical): Connecting different software systems so they can work together.
• Interactive Email (Design/Engagement/Technical): Emails with elements you can engage with.
• IP Address (Technical): A unique numerical label assigned to each device connected to a computer network.
• IP Reputation (Deliverability/Security): A "credit score" for your IP address based on email history.
• IP Warming (Deliverability): The practice of gradually increasing the volume of emails sent from a new IP address.
• ISP (Internet Service Provider) (Technical): Examples: Gmail, Outlook, Yahoo.

J

• JPEG/JPG (Design): A common image format for photos.
• Justified Text (Design): Text aligned evenly on both left and right margins.

K

• Kerning (Design/Typography): Adjusting space between individual letters.
• Keyframe Animation (Design/Technical): CSS code that creates motion.
• Kinetic Email (Design/Engagement/Technical): Interactive emails that allow recipients to perform actions within the email itself.
• KPI (Key Performance Indicator) (Performance Metrics): A measurable value that demonstrates how effectively a company is achieving key business objectives.

L

• Leading (Design/Typography): The vertical space between lines of text.
• LDAP (Lightweight Directory Access Protocol) (Technical): A protocol for accessing and maintaining distributed directory information services.
• Liquid Design (Liquid Layout) (Design): An email or website design that uses percentages for widths and adjusts fluidly to different screen sizes.
• List Broker (List Management): A company that sells or rents email lists.
• List Churn (List Management): The rate at which subscribers leave an email list.
• List Fatigue (List Management): When subscribers become disengaged or annoyed by receiving too many emails.
• List Hygiene (List Management): Cleaning your email list by removing inactive or invalid email addresses.
• List-Unsubscribe Header (Deliverability/Technical): A one-click unsubscribe button in the email header.
• Localization (Content): Adapting content to a specific region or language.
• Lorem Ipsum (Design): Placeholder text used to mock up designs before final copy is written.

M

• Mail Server (Technical): A computer system that sends and receives emails.
• Mailer Daemon (Technical): An automated email message from a mail server informing the sender about a delivery problem.
• Mailto (Technical): A type of HTML link that opens the user's default email program with the "To" field pre-filled.
• Margin (Design): Space outside an element.
• Marketing Automation Platform (MAP) (Marketing/Technical): A software platform used to automate marketing tasks and workflows.
• MarTech (Marketing Technology) (Marketing/Technical): The use of technology in marketing efforts.
• Media Queries (Design/Technical): A CSS technique that allows you to apply different styles for different screen sizes or devices.
• Metrics (Performance Metrics): Quantifiable measures used to track and assess the performance of marketing activities.
• Microinteractions (Design/Engagement): Small, subtle animations or feedback that occur when a user interacts with a website or app.
• MIME (Multipurpose Internet Mail Extensions) (Technical): An internet standard that extends the format of email to support text in character sets other than ASCII, as well as attachments.
• MIME Type (Technical): A standard way to indicate the format of a file on the internet.
• MJML (Mailjet Markup Language) (Technical/Design): A responsive email framework.
• MME (MIME Encapsulation of Aggregate Documents) (Technical): A format for bundling multiple parts into a single email message.
• Mobile First Design (Design): Designing emails for phones first.
• Mockup (Design): A preview of how an email will look.
• MTA (Mail Transfer Agent) (Technical): Software that transfers electronic mail messages from one computer to another.
• MUA (Mail User Agent) (Technical): An email client used by an end user to access and manage their email.
• Multilingual (Content): Supporting multiple languages.
• Multivariate Test (Performance Metrics): Testing multiple variations of different elements at the same time.
• MX Record (Mail Exchanger Record) (Technical/Deliverability): DNS settings that direct emails to your domain’s inbox.

N

• Navigation Bar (Design): A menu linking to your website’s key pages.
• Negative Space (Design): The empty or open space around and between elements in a design.
• Non-Responsive Design (Design): Emails that don’t adjust to screen sizes.
• Nurture (Marketing): Building relationships with potential customers by providing them with relevant information over time.

O

• ODBC (Open Database Connectivity) (Technical): A standard API for accessing database management systems.
• Omnichannel (Marketing): A marketing approach that provides a seamless and consistent brand experience across all available channels.
• Onboarding (Marketing): The process of guiding new users or customers through the initial stages of using a product or service.
• Open Rate (Performance Metrics/Engagement): The percentage of email recipients who opened an email.
• Opt-Out (List Management/Legal/Compliance): The process of unsubscribing or withdrawing consent to receive emails or have data collected.
• Outbound Marketing (Marketing): A traditional marketing approach where marketers reach out to potential customers directly.
• Outlook Rendering Issues (Technical/Design): Microsoft Outlook’s tendency to mangle email designs.
• Overlay Text (Design): Text placed on top of an image.

P

• Padding (Design): Space inside an element.
• PDF in Email (General Email Terms): Attaching a PDF (not recommended).
• Personalization (Content/Marketing): Tailoring email or website content to individual recipients based on their data and preferences.
• Phishing (Security/Privacy): Scam emails pretending to be trusted brands.
• Pishing (Security/Privacy): A misspelling of phishing, referring to fraudulent attempts to obtain sensitive information.
• Pixel (Design/Technical): A tiny dot of color; screen resolutions are measured in pixels.
• Plain Text (Technical): An email format that contains only text without any formatting.
• POP3 (Post Office Protocol version 3) (Technical): A protocol used to retrieve email from a mail server.
• Preheader Text (Design/Content): The preview text after the subject line.
• Preference Center (List Management): A page where email subscribers can manage their communication preferences.
• Preview Text (Design/Content): See Preheader Text.
• PRM (Partner Relationship Management) (Business): A system used to manage a company's relationships with its partners.
• Prospect (Marketing): A potential customer.
• Proxy (Technical/Security): A server that acts as an intermediary between a user's computer and the internet.
• PS (Postscript) (Content): An additional note at the end of an email.
• QA (Quality Assurance) (Workflow): The process of testing and ensuring the quality of emails or websites before they are launched.
• p=none (Monitor Mode): No action is taken on emails that fail DMARC; they are delivered normally, but reports are sent to the domain owner for monitoring.
• p=reject (Strict Protection): Emails that fail DMARC are completely rejected (not delivered to the recipient).

R

• Reengagement (Marketing/List Management): Efforts to reconnect with inactive subscribers or customers.
• Remarketing (Marketing): Showing ads to people who have previously visited your website.
• Rendering (Technical/Design): How an email or webpage appears in different email clients or web browsers.
• Responsive Design (Design): Emails that adapt to any screen size.
• Retention (Marketing): The ability to keep customers coming back and continuing to use a product or service.
• Retina Display (Design): High-resolution screens.
• Revenue Per Email Sent (RPE) (Performance Metrics): The average revenue generated from each email sent.
• "Recency, Frequency, Monetary (RFM)" (Marketing/List Management): A method used to segment customers based on their recent purchases, how often they purchase, and how much they spend.
• Return On Investment (ROI) (Performance Metrics): A measure of the profitability of an investment.
• ROMI (Return on Marketing Investment) (Performance Metrics): A specific type of ROI that measures the effectiveness of marketing campaigns.
• Router (Routing System) (Technical): A networking device that forwards data packets between computer networks.
• RGB Color (Design/Technical): A color model using red, green, and blue light.

S

• Safelist (Deliverability): A list of email addresses or domains that you trust.
• Sandbox (Technical): A testing environment to preview emails before sending.
• Sans Serif Fonts (Design/Typography): Clean fonts without serifs.
• Segmentation (List Management/Marketing): Dividing an email list or customer base into smaller groups based on shared characteristics.
• Sender Information (Technical): Details about the sender of an email, usually found in the email header.
• Sender Name (General Email Terms): The name that is displayed as the sender of an email in the recipient's inbox.
• Sender Reputation (Deliverability/Security): A score that ISPs assign to email senders based on their sending history and practices.
• Sender Score (Deliverability): A 0-100 rating of your IP’s reputation.
• Serif Fonts (Design/Typography): Fonts with small lines (serifs) at edges.
• SFTP (Secure File Transfer Protocol) (Technical): A secure way to transfer files between computers.
• Shared IP (Deliverability): An internet protocol (IP) address that is used by multiple senders.
• Shared Server (Technical): A server that hosts multiple websites or email accounts.
• Signoff (General Email Terms): A closing remark at the end of an email.
• Single Column Layout (Design): An email or website design that arranges content in a single vertical column.
• Single Opt-In (List Management): A process where a user subscribes to an email list with just one step.
• S/MIME (Secure/Multipurpose Internet Mail Extensions) (Security/Privacy/Technical): A standard for public key encryption and signing of MIME data.
• SMTP (Simple Mail Transfer Protocol) (Technical): A protocol used to send email between mail servers.
• Snail Mail (General Email Terms): Regular postal mail.
• Socials Tab (General Email Terms): A tab in some email inboxes where emails from social media platforms are grouped.
• Soft Bounce (Deliverability): An email that could not be delivered temporarily.
• Spam (Deliverability/Security): Unsolicited or unwanted email messages, often sent in bulk.
• Spam Trap (Deliverability/Security): Fake email addresses used to catch spammers.
  • Pristine (Deliverability/Security): Never used by a real person.
  • Recycled (Deliverability/Security): Abandoned addresses turned into traps.
• SPF (Sender Policy Framework) (Deliverability/Security): A "guest list" for your email domain.
• Spy Pixel (Tracking Pixel) (Technical/Performance Metrics): A small, often invisible image embedded in an email or webpage that is used to track whether an email has been opened or a page has been visited.
• SQL (Structured Query Language) (Technical): A language used for managing and manipulating databases.
• SSL (Secure Sockets Layer) (Technical/Security): A security protocol that provides encrypted communication between a web server and a web browser.
• SSO (Single Sign-On) (Technical/Security): A process that allows users to log in to multiple applications with a single set of credentials.
• Starring an Email (General Email Terms): Marking an email as important or needing attention in an email client.
• Stock Photo (Design): Generic images purchased for emails.
• Style Guide (Design/Branding): A document defining your email design rules.
• Subject Line (Content): The text that appears in the inbox and summarizes the content of an email.
• Sunsetting (List Management): Archiving inactive subscribers to keep your list fresh.
• Suppression List (List Management/Deliverability): A list of email addresses that should not receive emails.

T

• Tabular (Design): Arranged in a table format.
• TCP/IP (Transmission Control Protocol/Internet Protocol) (Technical): The fundamental communication protocols that underpin the internet.
• Template (Design): A reusable email layout.
• Thumbnail Image (Design): A small image linking to a larger version or webpage.
• Throttling (Deliverability): Limiting the rate at which emails are sent.
• TLS (Transport Layer Security) (Technical/Security): Encrypts email data.
• Tracking Pixel (Technical/Performance Metrics): See Spy Pixel.
• Trigger (Marketing Automation): An event that automatically initiates an action.
• Type Anatomy (Typography): The different parts of a letterform in typography.
• Typography (Design): The art of arranging text.

U

• Unicode (Technical): A universal character encoding standard.
• Unique Clicks (Performance Metrics/Engagement): The number of individual recipients who clicked on one or more links in an email.
• Unique Opens (Performance Metrics/Engagement): The number of individual recipients who opened an email.
• Unique Selling Proposition (USP) (Marketing): The unique benefit that differentiates a product or service from its competitors.
• Unsubscribe Button/Link (Legal/Compliance/List Management): A legally required link to opt out of emails.
• URL Parameter (Technical/Performance Metrics): A part of a web address that adds extra information, often used for tracking.
• UX (User Experience) (Design): How subscribers interact with and feel about your email.

V

• Variable (Personalization/Technical): A piece of information that can change, used to personalize email content.
• Vector Image (Design): Graphics made of paths (not pixels) that stay crisp at any size.
• View in Browser Link (Technical/Design): A backup link to see the email online if it doesn’t render properly.
• Vignette (Design): A gradual fade effect at the edges of an image.
• VPN (Virtual Private Network) (Technical/Security): A network that provides a secure and encrypted connection over a less secure network.

W

• Warm-up (Deliverability): Gradually increasing email volume from a new IP to build trust.
• Webhook (Technical): A way for an application to provide other applications with real-time information whenever a certain event happens.
• Web Fonts (Design/Technical): Custom fonts embedded via services like Google Fonts.
• Webmail (Technical): An email service that can be accessed through a web browser.
• Web View (Technical/Design): A link in an email that allows recipients to view the email in a web browser.
• Whitelist (Deliverability): See Allowlist.
• Whitespace (Design): See Empty Space.
• Wireframe (Design): A basic sketch of an email’s layout.
• WYSIWYG (What You See Is What You Get) (Design): An editor that allows you to see what the final output will look like while you are creating it.

X

• XHTML (Technical): A stricter version of HTML used in older email designs.

Z

• Z-Pattern Layout (Design): A design where readers’ eyes scan the email in a "Z" shape.
• Zero-Day Spam (Deliverability/Security): New spam tactics that filters haven’t learned to block yet.
• Zoom (Design/Accessibility): How subscribers enlarge email text on mobile.