Email marketing glossary.

186 plain definitions, from open rates and CTR to DKIM authentication and behavioral triggers. Search a term or browse by letter.

186 terms

A

A/B Split Test, also known as Split Test, TestAn A/B split test is when you send two versions of an email to different groups to see which one gets better results. You change one thing at a time and then pick the version that performs best.
Abandoned Cart Email, also known as Cart Abandonment Email, Cart Recovery EmailAn automated email that goes out when someone adds items to their cart but leaves without buying. These emails show what they left behind and usually include a direct link back to their cart. Most businesses send a series of 2-3 reminders over a few days, sometimes sweetening the deal with a discount or free shipping offer.
Acceptable Use Policy, also known as AUPAn Acceptable Use Policy (AUP) is a set of rules defined by an ESP or ISP that governs what type of content and behavior is allowed on their network.
AccessibilityMaking your emails easy to read and use for everyone, including people with disabilities. It covers things like clear layout, readable text, helpful alt text, and strong color contrast.
Alternative Text, also known as Alt Text, Descriptive TextShort text that explains what an image shows and why it is in your email. It helps people and email clients understand your message when the image does not load.
AMP, also known as AMP Email, AMP4Email, Accelerated Mobile Pages, ⚡️AMP is a Google tech that makes emails interactive, so people can do things like submit forms or browse products without leaving the inbox. It only works in a few email clients, so you always need a normal HTML fallback.
AMPscriptAMPscript is Salesforce Marketing Cloud's scripting language for personalizing each email with data from your subscriber records. It runs at send time so every person gets content that matches their details and behavior.
AnalyticsThe practice of tracking what happens after you hit send on your email campaigns. Analytics shows you who opened, who clicked, who bought, and who bounced—turning guesswork into data-driven decisions about what's actually working in your email program.
Animated GIF, also known as GIF, JIFAn animated GIF is a short, looping image that feels like a tiny video in an email. It starts playing as soon as the email opens and works in most inboxes without extra clicks.
API, also known as Application Programming InterfaceA way for different software tools to talk to each other. In email marketing, APIs let your website, app, and email platform share data automatically so information stays in sync without extra work.
ApprovalThe formal sign off from the people who must review your email before it goes out. It is the step where stakeholders confirm the content is correct, safe, and on brand.
AttachmentA file that travels with an email message, like a PDF or image. Attachments are fine for one-to-one emails but risky for bulk marketing sends because they can hurt deliverability.
AttributionAttribution is how you connect revenue or signups back to the emails and touchpoints that helped cause them. It helps you see which campaigns actually drive results so you can spend time and budget on what works.
Authenticated Received Chain (ARC), also known as ARC, Email ARCAuthenticated Received Chain (ARC) is an email standard that keeps your authentication results when a message is forwarded or passes through mailing lists. It lets receiving servers see that earlier checks passed even if SPF or DKIM now look broken.
AuthenticationThe process of proving to inbox providers that your emails really come from your domain. It helps stop spoofing and keeps more of your messages out of spam.
Autoresponder, also known as Out of Office, OOO, Auto-replyAn autoresponder is an automatic email that sends right after someone takes an action, like emailing you or filling out a form. It confirms what they did and tells them what will happen next.
Average Order Value (AOV), also known as AOV, Average Transaction ValueAverage order value is the average amount a customer spends on each order. You calculate it by dividing total revenue by the number of orders.

B

Backscatter, also known as Blowback, collateral spamBackscatter is when a mail server sends bounce messages to an innocent third party because their email address was spoofed by a spammer.
Batch Email, also known as Batch Send, Bulk SendBatch email is when you send the same email to many people at once. Your email platform sends it in groups so you can reach a large list without hurting deliverability.
Behavioral Targeting, also known as Behavior-Based Targeting, Action-Based TargetingBehavioral targeting means sending emails based on what people do, not just who they are. You use actions like pages visited, products viewed, and purchases to decide which message to send next.
Behavioral Trigger, also known as Behavior-Based Trigger, Action TriggerAn automated email that sends when someone does something specific on your site or in your product. It reacts to real behavior so the message matches what they just did.
BIMIBrand Indicators for Message Identification (BIMI) lets your verified logo appear next to your emails in inboxes that support it. It gives people a clear visual signal that the message really comes from your brand.
Blacklist, also known as Blocklist, DenylistAn email blacklist is a list of IP addresses or domains that inbox providers treat as unsafe. If you are on one, your emails are more likely to land in spam or get blocked before they arrive.
Blast, also known as Campaign, SendAn old term for sending one bulk email to many people at once. It often suggests a generic, untargeted message instead of a thoughtful campaign.
Blocklist, also known as BlacklistA blocklist is a list of IP addresses or domains that are known for sending bad or unwanted email. If you are on a blocklist, inbox providers often block or filter your messages before anyone can see them.
Bounce (Hard)Hard bounce is when an email cannot be delivered because the address is invalid or blocked. It is a permanent failure and the address should be removed from your list.
Bounce (Soft)A soft bounce is when an email fails to deliver for a temporary reason, like a full inbox or a short outage at the recipient mail server. The address is still valid, and the email may be delivered if you try again later.
Bounce Rate, also known as Email Bounce RateBounce rate is the percentage of emails that could not be delivered to recipients. It shows how many addresses are invalid or blocked compared to the total you tried to send.
Branching, also known as Workflow Branching, Path BranchingBranching is when an automation splits into different paths based on a person's data or actions. It sends people into different email flows so messages feel more relevant.
Broadcast, also known as Broadcast Email, Mass EmailA one time email you send to your whole list or a segment at a single time. You write it once, choose who should get it, and it sends when you press send.
Browse Abandonment, also known as Browse Abandonment Email, Product View AbandonmentBrowse abandonment is when someone views products on your site but leaves without adding anything to their cart or buying. A browse abandonment email is an automated follow up that reminds them what they saw and invites them back.
Bulk Mail, also known as Bulk Marketing, BlastBulk mail is sending one email to a large group of people at the same time, usually without segmentation or deep personalization. It is a simple way to reach many subscribers with one message.

C

California Consumer Privacy Act (CCPA), also known as CCPAA California privacy law that gives residents clear rights over how businesses collect, use, and share their personal data. It applies to larger companies and those that handle a lot of data from people who live in California.
Call-To-Action (CTA), also known as CTAThe button or link in your email that tells people exactly what to do next. Usually short, direct text like "Shop now" or "Start my free trial" that makes the next step clear.
Campaign, also known as Email Campaign, Marketing CampaignA campaign is a planned set of emails that work together toward one clear goal. Each email supports the same outcome and is sent to a defined audience over a set period.
CAN-SPAMCAN-SPAM is the main email marketing law in the United States. It sets the basic rules for how you can send commercial email and how people can opt out.
CASLCanada's Anti-Spam Legislation. It sets clear rules for how you collect consent and send marketing emails to people in Canada.
Catch-All, also known as Accept-allA catch-all is a server configuration that accepts emails sent to any address at a domain, even if the specific mailbox doesn't exist.
Click Rate (CR), also known as Click Through Rate, CRThe percentage of delivered emails where someone clicks a link. It shows how many people take action from your email.
Click To Open Rate (CTOR), also known as CTORThe percentage of people who opened your email and then clicked a link inside. It shows how engaging your content is after someone opens.
Click-Through Rate (CTR), also known as CTR, Click RatePercentage of delivered emails where someone clicked a link. It is a simple way to see how many people move from reading your email to taking action.
Complaint, also known as Spam ComplaintWhen someone clicks the spam or junk button on your email instead of unsubscribing. That action tells inbox providers your email was unwanted and counts as a complaint against your sending reputation.
Complaint Rate, also known as Spam Complaint Rate, Abuse RateThe percentage of people who mark your emails as spam. It shows how many subscribers see your message as unwanted and affects whether future emails reach the inbox.
Conditional Logic, also known as If/Then Logic, Branching LogicConditional logic is the if/then rules in your email automation that choose what to send based on what each person does or does not do. It helps you send different emails to people in the same flow so each message feels more relevant.
Consent, also known as PermissionClear permission someone gives you to send them email. It means they understand what they signed up for and have agreed to get messages from you.
Conversion Goal, also known as Goal, Automation Goal, Workflow GoalA conversion goal is the action you want someone to take after your email. It shows that your automation did its job and led to a clear result you can track.
Cost Per Mile (CPM), also known as Cost Per Mile, Cost Per Thousand, CPTCPM is what you pay to send 1,000 emails through a provider. It shows your cost per thousand sends so you can compare pricing between tools.
CSS, also known as Cascading Style SheetsCSS is the styling code that controls how your emails look, including fonts, colors, spacing, and layout.
Customer Acquisition Cost (CAC), also known as CACThe average amount you spend to win one new paying customer. It includes your marketing, sales, and related costs over a period divided by how many new customers you gained.
Customer Journey, also known as Journey, User Journey, Email JourneyA customer journey is the path someone takes from first hearing about your brand to becoming a repeat buyer. In email marketing, it is the series of emails and touch points they receive over time.
Customer Lifetime Value (CLV), also known as CLV, LTV, Lifetime ValueThe total money a customer is expected to spend with your business from their first purchase until they stop buying. It helps you decide how much you can afford to spend to win that customer and keep them coming back.

D

Dark ModeDark mode is a display setting where email apps switch light backgrounds to dark ones and flip text colors so emails feel easier to read in low light.
Data Retention, also known as Data Retention Policy, Retention PeriodHow long you keep customer and email data before you delete it. It sets clear rules for when you remove or anonymize contact and activity data so you only hold what you actually need.
Dedicated IP, also known as Dedicated ServerAn IP address used only by your business to send email. It helps higher volume senders control their own reputation instead of sharing it with others.
Dedicated Server, also known as Dedicated IPA dedicated server is a private email server with its own IP address that only your company uses to send email. It gives you direct control over your sender reputation and delivery results.
Deferral, also known as Temporary failure, 4xx error, soft bounceA deferral is when a receiving email server temporarily refuses a message but suggests trying again later.
Deliverability, also known as Email Deliverability, Inbox PlacementDeliverability is how often your emails land in the inbox instead of spam or getting blocked. Strong deliverability means people actually see what you send and can act on it.
Delivery Rate (DR), also known as DRDelivery rate is the percentage of emails that are accepted by recipients' mail servers without bouncing. It shows how many of your sent emails clear the technical checks so they can be placed in a mailbox.
Design SystemA design system is a shared set of reusable email building blocks and rules your team uses to create emails. It keeps layouts, styles, and code consistent so you can build emails faster.
Disposable Email, also known as Burner email, throwaway addressA disposable email is a temporary address created for a single use, often to sign up for a service without revealing a real address.
DKIM, also known as DomainKeys Identified MailDKIM is a way to sign your emails so receiving servers can confirm they came from your domain and were not changed on the way.
DMARC, also known as Domain-based Message Authentication Reporting and ConformanceDMARC is an email security policy that tells receiving mail servers what to do when messages from your domain fail SPF or DKIM checks. It helps stop spoofing and gives you reports about who is sending email using your domain.
Domain ReputationHow trusted your sending domain is by email providers like Gmail and Outlook. A strong domain reputation keeps your emails in the inbox instead of spam.
Double Opt-In, also known as Confirmed Opt-In, COIWhen someone signs up, you send a confirmation email and only add them after they click the link. It adds a small extra step but keeps your list clean and engaged.
Drip Campaign, also known as Drip Sequence, Email Drip, Automated SequenceA series of pre-written emails that automatically go out over time, like a slow drip from a faucet. You write them once, set the schedule, and they nurture leads on autopilot. Someone signs up today, they get email 1. Three days later, email 2. A week later, email 3. Perfect for welcoming new subscribers, educating prospects, or onboarding customers without lifting a finger.
Dynamic Content, also known as Live Content, Real-time ContentDynamic content is email content that updates based on who is viewing it or when they open it. It can pull in data like products, offers, or status in real time so one email feels tailored to each person.

E

Email Alias, also known as Plus AliasAn email alias is a version of your email address that still delivers to the same inbox. It lets you create different addresses for signups and tracking without managing more accounts.
Email AppendingEmail appending is when you use a third party to add email addresses to your existing customer records based on other details like name or postal address. It is risky because these people did not ask to hear from you, which often leads to spam complaints and poor deliverability.
Email Client, also known as Email Program, Email App, ClientSoftware or apps people use to read, send, and manage email, such as Gmail or Apple Mail. Different email clients can display the same email in different ways, which affects how your emails look and perform.
Email Engagement Score, also known as Engagement Score, Subscriber Engagement ScoreA simple score that shows how active a subscriber is with your emails, based on actions like opens, clicks, replies, and purchases. It helps you quickly see who is engaged and who might be slipping away.
Email GeekAn email geek is someone who loves the craft of email and works to make every send better. They test ideas, care about deliverability, and treat subscribers like real people, not just numbers on a list.
Email Header, also known as Message Header, Email MetadataAn email header is the technical information attached to every email that shows where it came from and how it moved between servers. It also records checks that help decide whether the message is safe and legitimate.
Email MarketingEmail marketing is the practice of sending emails to groups of people to build relationships and drive actions like sales or sign ups.
Email Sequence, also known as Email Series, Message SequenceAn email sequence is a planned set of emails that send automatically after someone takes a specific action, like signing up or buying. It helps you guide subscribers through a simple journey without sending every email by hand.
Email Service Provider (ESP), also known as ESP, Email Platform, Marketing Automation PlatformThe software you use to send and manage email campaigns. It stores your contacts, sends messages in bulk, and tracks what happens after you hit send.
EmojiSmall icons like 😊 or 🎉 that you add to subject lines and email copy so your message is easier to notice and understand. They act as simple visual cues that show tone and make your emails feel more personal.
EngagementThe actions people take with your emails, like opens, clicks, replies, forwards, and time spent reading. Strong engagement shows that your audience is paying attention and wants to hear from you.
Engagement Rate, also known as Email Engagement Rate, Overall EngagementThe share of your email subscribers who interact with what you send through opens, clicks, replies, or other actions. It gives you a quick read on how healthy and relevant your email program is.
EnvelopeThe email envelope is everything someone sees about your email in their inbox before they open it. It includes the sender name, subject line, and preview text that guide their choice to open or ignore it.
Event Trigger, also known as Trigger, Automation TriggerA specific action or change that tells your email system to start an automation. It can be a sign up, a purchase, a page view, or a data update that kicks off a workflow.

F

Feedback Loop (FBL), also known as FBL, Complaint Feedback LoopA feedback loop is a system where inbox providers tell you when someone marks your emails as spam. It gives you a clear signal so you can remove complainers fast and protect your sender reputation.
Forward, also known as Forward To A Friend, FTAFWhen someone shares your email with another person by clicking forward in their email client or using a forward to a friend link in your email. It is a strong signal that they found your message useful, but manual forwards often break tracking so many teams prefer using dedicated forward to a friend features instead.
Forward Rate, also known as Share Rate, Email Forward RateForward rate is the percentage of delivered emails that people share or forward to others. It shows how many subscribers liked your email enough to pass it on.
From Address, also known as From Field, Sender AddressThe email address people see as the sender in their inbox. It tells them who the message is from and helps them decide whether to open it.
FunnelA funnel is the path someone follows from first hearing about you to becoming a customer. It breaks that journey into stages so you can send the right email at the right time.

G

GDPRThe General Data Protection Regulation is Europe's privacy law that sets rules for how you collect, store, and use personal data from people in the EU. It shapes how you build email lists, send marketing messages, and handle requests about data access or deletion.
Google Postmaster Tools, also known as GPTGoogle Postmaster Tools is a free dashboard provided by Gmail that shows senders data about their domain reputation, spam rate, and authentication.
GreylistingGreylisting is an anti-spam technique where a receiving server temporarily rejects emails from unknown senders to test if they are legitimate.

H

HELO/EHLOHELO and EHLO are the commands a sending server uses to identify itself at the start of an SMTP conversation.
Honey PotA honey pot is a fake email address used by inbox providers and anti spam groups to spot senders with bad list practices. Sending to these addresses hurts your reputation and makes it harder for your emails to reach the inbox.
HTMLHTML is the code that shapes how your email looks and feels in the inbox. In email marketing it uses a simpler, stricter version of web HTML so your design works across many different clients.

I

Image BlockingWhen email clients stop images from loading automatically, so people see empty boxes or alt text instead of pictures. This protects users from tracking and unsafe content, so you should never rely only on images to tell your message.
Inbox Placement Rate, also known as IPR, Inbox Rate, Delivery RateInbox placement rate is the percentage of your sent emails that land in the inbox instead of spam or getting blocked. It shows how often your messages actually reach people.
InclusionMaking your emails easy to understand and use for many different people. It means thinking about language, images, and layout so more people feel welcome and able to take action.
IntegrationConnecting your email platform to other tools so data moves between them and can trigger emails at the right time.
Internet Service Provider, also known as ISPCompanies that provide internet access and often email services to people and businesses. In email marketing, they decide if your emails reach the inbox or land in spam.
IP Warming, also known as Server WarmingIP warming is the process of slowly increasing email volume from a new IP so inbox providers learn to trust it. You start with small sends to engaged contacts and raise the volume over a few weeks.

K

Kinetic Email, also known as Interactive EmailKinetic email is an interactive email that lets people click, swipe, or tap inside the message instead of going to a web page. It uses HTML and CSS to create simple actions like carousels, accordions, or quick surveys right in the inbox.

L

Lead Scoring, also known as Lead Score, Prospect ScoringLead scoring ranks your leads by how interested and ready to buy they seem based on simple scores from their actions. It helps you see warm leads fast so you can focus your time where it makes the most sense.
List, also known as Audience, SegmentYour email list is the group of people who have asked to hear from you by email. It is an audience you own and can contact any time without relying on ads or social platforms.
List Broker, also known as List Dealers, SpammersCompanies or people who sell or rent email lists to marketers. Buying from them is risky because contacts never asked to hear from you and you can hurt deliverability or break the law.
List Churn, also known as ChurnThe percentage of subscribers you lose from your email list in a set time period. It includes people who unsubscribe, mark you as spam, or are removed because their address no longer works.
List FatigueList fatigue is when your email subscribers tune out because they see too many emails or content that does not feel useful. They stop opening, clicking, and buying, which hurts your results over time.
List Growth Rate, also known as Email List Growth, Subscriber Growth RateThe speed your email list grows or shrinks over time, shown as a percentage. It includes both new subscribers and people who leave, so you see your real list change.
List HygieneList hygiene is the practice of cleaning your email list by removing bad or inactive addresses. It keeps your list focused on people who still want your emails.
List-Unsubscribe, also known as One-click unsubscribeList-Unsubscribe is an email header that allows recipients to unsubscribe from a mailing list without searching for a link in the footer.
LocalizationMaking your emails feel natural in different countries and cultures. You adjust language and key details so each audience feels the message was made for them.

M

Mail Loop, also known as Routing loopA mail loop occurs when an email is forwarded back and forth between servers without ever reaching a final destination.
Marketing AutomationMarketing automation uses rules and triggers to send emails based on what people do. It saves time and keeps your messages timely and relevant.
Marketing Automation Platform (MAP), also known as MAPSoftware that helps you send the right messages to people based on what they do. It automates emails and other marketing tasks so you do not have to do them by hand.
MarTech, also known as Marketing TechnologyThe tools and software you use to plan, run, and track your marketing across channels. It covers everything from email platforms to analytics and CRM so your work is connected instead of scattered.
Message Transfer Agent (MTA), also known as MTA, Mail Transfer Agent, Mail ServerA Message Transfer Agent is the server that moves email from one mail system to another. It takes outgoing messages from your email tool and hands them off to the next mail server using SMTP until they reach the right inbox.
MetricsEmail metrics are the numbers that show how your campaigns perform. They make it clear how many people open, click, and buy from your emails.
MIME Type, also known as MIMEMIME types are labels that tell email clients what kind of content each part of a message holds. They make sure text, HTML, images, and attachments show up the way you expect.
MTA-STS, also known as Mail Transfer Agent Strict Transport SecurityMTA-STS is a security standard that allows a domain to force authentication and encryption for inbound emails.
Multi-Touch Attribution, also known as MTA, Attribution ModelingMulti-touch attribution tracks all the marketing touches that lead to a sale and shares credit between them. It shows the full path a customer takes instead of only the first or last click.
Multivariate TestTesting different versions of several email elements at the same time to find the best mix. Instead of changing only one thing, you compare full combinations to see which gets the most opens, clicks, or sales.

N

Newsletter, also known as Email Newsletter, Regular NewsletterAn email newsletter is a regular email you send to subscribers with updates, ideas, and useful content. It keeps a steady connection with your audience between launches or promotions.
NurtureNurture means building a relationship with people on your list through helpful, well timed emails. The goal is to move them closer to buying while keeping existing customers active and happy.

O

OmnichannelOmnichannel means your customer experience feels joined up across email, your site, ads, and support, so every touchpoint shares the same view of the customer. It uses shared data to keep messages consistent and relevant no matter where someone interacts with you.
Onboarding, also known as Welcome SeriesThe emails you send to new subscribers or customers in their first days with you. Onboarding sequences welcome them, show what they can do next, and help them get value fast.
Open Rate (OR)The percentage of delivered emails that people open. Useful as a quick health check on subject lines and inbox placement, but it does not show real engagement on its own.
Open Relay, also known as Insecure relayAn open relay is an email server configured to allow anyone on the internet to send email through it, regardless of who they are.
Opt-OutAn opt-out is when someone on your email list chooses to stop getting your emails and uses a clear way to unsubscribe or change their settings. You must respect this choice quickly to stay compliant and protect your sender reputation.

P

PersonalizationPersonalization means tailoring your emails to each person based on what you know about them. You use details like their name, past purchases, and behavior so your emails feel relevant instead of generic.
Plain TextPlain text emails contain only text without images, buttons, or design, so they look like a normal personal message. They are simple to create and often feel more authentic, but you give up detailed tracking and visual branding.
Post-Purchase Email, also known as Post-Purchase Follow-Up, Order Confirmation Follow-UpThe series of emails you send customers after a purchase to confirm the order, share updates, and support them after they buy.
Preference Center, also known as Preferences Page, Unsubscribe PageA preference center is a simple page where subscribers choose which emails they still want to get from you. It lets people change topics or frequency instead of leaving your list completely.
Preview Text, also known as Preheader TextShort line of copy that appears next to or under your subject line in the inbox. Usually pulled from the email body and used to give people a reason to open.
Privacy and Electronic Communications Regulations (PECR), also known as PECR, UK PECRPECR is the UK law that covers email, SMS, calls, and other digital marketing. It sets clear rules for consent, marketing messages, cookies, and other tracking.
Privacy Policy, also known as Privacy Notice, Data Protection PolicyYour privacy policy explains what data you collect from people, how you use it, and how you keep it safe. It sets clear expectations so subscribers know what happens when they share their email and other details with you.
Promotions Tab, also known as Promo Tab, Promotions FolderThe Promotions tab is the place in Gmail where most marketing and sales emails appear. It keeps discounts, offers, and brand updates in one spot so people can check them when they want to shop.
PTR Record, also known as Pointer recordA PTR record is a type of DNS record that maps an IP address to a domain name, used for Reverse DNS.

Q

QA, also known as Testing, ApprovalsQuality Assurance for email. It is the process of checking each campaign before you send it so you catch mistakes early.

R

Recency, Frequency, Monetary (RFM)RFM is a way to score customers based on how recently they bought, how often they buy, and how much they spend. It helps you spot your best customers quickly and see who might be slipping away.
Reengagement, also known as Win BackReengagement is the process of running a short email campaign to people who stopped opening or clicking your emails. The goal is to either win them back or remove them cleanly from your list.
Relay Access Denied, also known as 554 5.7.1"Relay Access Denied" is a common error message indicating that a mail server refused to let you send email through it because you are not authorized.
Reply-To, also known as Reply To AddressThe email address where replies to your message are sent. It can be different from the From address so replies land with the right person or team.
Reputation, also known as Sender ReputationSender reputation is the trust score mailbox providers give your emails based on how you send and how people react. It helps decide if your messages land in the inbox or get pushed to spam.
Responsive EmailAn email design that adjusts to any screen size so it stays easy to read and click on phones, tablets, and desktops.
RetentionRetention is how well you keep customers coming back after their first purchase. It is about staying in touch so they stay active, buy again, and do not churn.
Return-Path, also known as Bounce Address, Envelope FromThe technical email address that collects bounces and delivery failure notices. It is separate from the visible From address and helps mail servers track delivery issues and clean up bad addresses.
Revenue Per Email Sent (RPE), also known as RPERevenue Per Email Sent (RPE) tells you how much money you make on average from each email you send. You find it by dividing the money from a campaign by the number of emails sent.
Reverse DNS, also known as rDNS, FCrDNSReverse DNS is the process of resolving an IP address back to a domain name, the opposite of standard DNS lookup.
Role Account, also known as Role-based email, functional addressA role account is an email address managed by a job function or a group rather than a specific person, such as admin@ or support@.

S

Safelist, also known as Whitelist, Safe Sender ListA safelist is a list of email addresses or domains that a person marks as trusted so their emails skip spam filters and go straight to the inbox. It tells the email provider to treat those messages as safe and deliver them to the main inbox.
Seed List, also known as Seed Addresses, Test InboxesA seed list is a small group of test email addresses you add to campaigns so you can see if messages land in the inbox, spam, or other folders before you send to your full list.
Segmentation, also known as Segment, GroupSegmentation means splitting your email list into smaller groups so you can send messages that match what each group cares about. It helps you talk to the right people instead of blasting the same email to everyone.
Send Time Optimization, also known as STO, Optimal Send Time, Best Time to SendA feature that chooses the best time to send each email based on when a person usually opens and clicks your messages.
Sender ScoreSender Score is a 0 to 100 rating of your sending reputation. A higher score means inbox providers are more likely to trust your emails and keep them out of spam.
Shared IP, also known as Shared ServerA shared IP is an IP address that many companies use to send email. Your messages go out from the same address as other senders on your platform, so your reputation is linked to how that group behaves.
Shared Server, also known as Shared IPA shared server is an email server and IP address that many companies use to send their emails. Your messages go out from the same place as other senders, so you share the same reputation.
Single Opt-InSingle opt-in is when someone joins your email list with one simple step. They fill out a form, hit submit, and start getting your emails right away.
Smart Host, also known as Relay host, smarthostA smart host is an intermediate mail server that relays email on behalf of another server, often to improve deliverability.
SMTPSMTP (Simple Mail Transfer Protocol) is the standard way email servers send messages to each other. It handles the handoff from your email tool to the recipient's mail server so messages can land in the inbox.
SMTP Banner, also known as Service bannerThe SMTP banner is the initial text greeting a mail server sends when a connection is first established.
SNDS, also known as Smart Network Data ServicesSNDS is a reputation monitoring portal provided by Microsoft to help senders track their IP health on Outlook.com and Hotmail.
SpamSpam is any email sent to someone without their clear permission or after they have lost interest in hearing from you. It is email that feels unwanted or irrelevant to the person receiving it.
Spam Trap, also known as Honeypot Address, Trap AddressA spam trap is an email address used by inbox providers to spot bad or careless senders. Hitting one damages your sender reputation and makes it more likely your emails go to spam.
SPFSender Policy Framework is a DNS setting that lists which servers can send email for your domain so inbox providers can quickly check if a message is real or spoofed.
Spy Pixel, also known as Tracking Pixel, Tracking BugA spy pixel is a tiny invisible image in an email that tracks when someone opens it. It helps email marketers measure open rates in a simple way.
STARTTLS, also known as Opportunistic TLSSTARTTLS is an email protocol command that upgrades a plain text connection to an encrypted one (TLS/SSL).
Subject LineA subject line is the short title of your email that shows up in the inbox. It gives people a quick idea of what the email is about and helps them decide if they will open it or ignore it.
Subscriber, also known as RecipientA subscriber is someone who gave you clear permission to receive your emails. They chose to join your list and expect useful, relevant messages from you.
Suppression List, also known as Exclusion ListA suppression list is the place your email tool keeps addresses that should not receive messages. It is a permanent "do not send" list that helps you avoid emailing people who have opted out or caused issues in the past.

T

TemplateA reusable email layout you use as a starting point for campaigns. It keeps your design consistent so you only need to update the content each time.
Test List, also known as Test Segment, Preview ListA test list is a small group of people who receive your email before everyone else. It is a simple way to spot problems before a full send.
Throttling, also known as Rate LimitingThrottling is when inbox providers or your email platform slow or limit how many emails you can send in a set time. It acts like a speed limit so big sends do not overwhelm their systems or hurt your reputation.
Time Zone Optimization, also known as Time Zone Targeting, Geographic Send TimeTime zone optimization is automatic scheduling that sends each email at a normal hour in the subscriber's own time zone so messages land when they are most likely to check their inbox. It uses location or time zone data to stagger the send across regions.
TrackingTracking is how your email tool logs opens, clicks, and sales that come from your emails. It helps you see what people do after they receive a message so you can improve future campaigns.
Transactional Email, also known as Transaction Email, System EmailTransactional emails are automatic messages sent when someone does something on your site or app, like placing an order or resetting a password. They share the key details about what just happened so people are not left guessing.
Triggered EmailA triggered email is a message your system sends automatically when someone does something specific, like signing up, leaving items in a cart, or reaching a milestone. It goes to one person based on their action instead of going to your whole list at a fixed time.

U

Unique ClicksThe number of unique subscribers who click at least one link in your email. Each person is counted once, even if they click several times.
Unique OpensUnique opens is the count of individual people who opened your email at least once. Each person is only counted one time, even if they open the same email many times.
Unsubscribe, also known as Opt OutThe action someone takes to stop getting your emails, usually by clicking a link at the bottom of a message. It is required by law and it shows respect when you stop emailing them right away.
Unsubscribe Rate, also known as Unsub Rate, Opt-Out RateThe unsubscribe rate is the percent of delivered emails that lead to an unsubscribe. It shows how many people no longer want to hear from you after a send.
URL, also known as LinkA URL (Uniform Resource Locator) is the web address behind a link in your email. It is what subscribers click to move from your message to a page on your site.
URL Parameter, also known as Tracking Parameter, Query StringsURL parameters are the text that comes after the "?" in a link. They tag where a click came from and what someone does on your site so you can see how each email link performs.

V

VersionA version is a specific saved state of an email or template. It lets you compare different drafts in tests and return to a known good setup if new changes do not work.

W

Wait Step, also known as Delay, Pause Step, Time DelayA wait step is a delay in an email automation that holds the next action for a set amount of time. It keeps messages spaced out so subscribers are not hit with too much at once.
Web View, also known as Web LinkA web view is the browser version of your email that opens in a normal web page. It gives people a clear way to read your message if their email client breaks the layout.
Welcome Email, also known as Welcome Message, First EmailThe first email a new subscriber gets right after joining your list. It introduces your brand and confirms what they can expect from you.
Whitelist, also known as Allowlist, Safe Sender ListAn email whitelist is a list of trusted senders or domains that people or email systems approve so their messages go to the inbox instead of spam. It is the opposite of a blocklist.
WireframeA wireframe is a simple sketch of your email layout that maps out where each key element sits before you design it. It helps you plan the structure without getting caught up in colors, fonts, or final copy.
Workflow, also known as Automation Workflow, Email WorkflowAn email workflow is an automated series of emails that sends itself based on what a person does or does not do. It uses simple rules to send the right message at the right time without manual work.
WYSIWYG, also known as What You See Is What You Get, Visual Editor, Live View, Design ViewA WYSIWYG editor lets you build emails by dragging and typing while you see the final layout as you work. It shows a live preview so you do not need to touch HTML.

More references.

SMTP field manual.

Every SMTP reply code, with real bounces from mailbox providers and spam filters and who needs to act.

Bounce playbooks.

Step-by-step fixes for bounces from Gmail, Yahoo, Outlook, Apple, and more, plus what each provider expects from senders.

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