Email marketing terminology is the shared language of metrics, acronyms, and concepts that marketers use to plan campaigns, protect deliverability, automate sends, authenticate their domains, and stay compliant. Knowing these terms is the difference between guessing at a report and acting on it. This glossary defines 162 terms across nine practical categories, written so you can find, understand, and apply each one quickly.
Table of Contents
Key Takeaways
- Email marketing terminology covers nine areas: core concepts, performance metrics, list management, automation, design, deliverability, authentication, privacy, and technical infrastructure.
- Delivery rate and deliverability are not the same. One measures acceptance, the other measures inbox placement.
- Open rate has become less reliable because privacy features preload images, so pair it with click and conversion data.
- Authentication protocols SPF, DKIM, and DMARC are now mandatory for bulk senders to Gmail and Yahoo.
- Good list hygiene, clear consent, and a working unsubscribe underpin both compliance and inbox placement.
Why Email Marketing Terminology Matters
Email marketing terminology matters because every decision in a campaign depends on reading signals correctly. A rising bounce rate, a falling click-to-open rate, or a failed DMARC check each points to a different fix. Marketers who understand the vocabulary diagnose problems faster, brief vendors clearly, and evaluate platforms on the criteria that affect results. This glossary groups terms the way real workflows use them, so related concepts sit together.
Key Email Metrics at a Glance
These are the metrics you will read on nearly every campaign report. Definitions and formulas appear here for quick reference, with fuller entries in the sections below.
| Metric | What It Measures | How It Is Calculated |
| Open rate | Share of delivered emails opened | Unique opens / delivered emails |
| Click-through rate (CTR) | Share of delivered emails clicked | Unique clicks / delivered emails |
| Click-to-open rate (CTOR) | Content and CTA strength among openers | Unique clicks / unique opens |
| Conversion rate | Share who completed the goal | Conversions / delivered emails |
| Bounce rate | Share of sends that failed delivery | Bounces / total emails sent |
| Unsubscribe rate | Share who opted out | Unsubscribes / delivered emails |
| Spam complaint rate | Share who marked as spam | Complaints / delivered emails |
Core Email Marketing Terminology
These foundational terms describe the people, parts, and message types that make up an email program.
Email marketing: The practice of sending commercial or informational messages by email to a list of subscribers to build relationships, promote offers, or drive action.
Email campaign: A single email or coordinated series sent to a list or segment to achieve a specific goal, such as a launch, sale, or newsletter issue.
Email service provider (ESP): A platform that stores contacts, builds and sends campaigns, and reports on results. ESPs range from simple newsletter tools to full automation suites. Our breakdown of essential email marketing features covers what to expect at each level.
Subscriber: A person who has opted in to receive email from a sender.
Contact: Any record in an email database, whether subscribed, unsubscribed, or unconfirmed.
Recipient: The person an email is delivered to.
Sender: The individual or brand sending an email, identified by the from address and sender name.
Sender name (friendly from): The display name recipients see in the inbox, separate from the underlying email address.
From address: The email address a message is sent from. It affects authentication, trust, and delivery.
Reply-to address: The address that receives replies, which can differ from the from address.
No-reply address: A from address that does not accept replies, such as noreply@brand.com. It is discouraged because it blocks two-way engagement.
Subject line: The short headline shown in the inbox that heavily influences whether an email is opened.
Preheader (preview text): The snippet shown after the subject line in many inboxes, used to extend the subject’s message.
Email body: The main content of the message, including text, images, and calls to action.
Call to action (CTA): The button or link that tells the reader what to do next, such as “Shop now” or “Read the guide.”
Newsletter: A recurring email that shares updates, content, or curated information rather than a single promotion.
Promotional email: An email designed to drive a purchase or response, such as a sale, discount, or launch.
Transactional email: A message triggered by a user action, such as a receipt, password reset, or shipping notice. It is expected by the recipient and usually exempt from marketing unsubscribe rules. See our guide to transactional email delivery for how it differs operationally from marketing sends.
Broadcast (blast, batch-and-blast): A single email sent to an entire list at once without segmentation or triggers.
Bulk email (mass email): High-volume sending to large lists, which raises the importance of authentication and reputation. Platforms diverge sharply at scale, as our comparison of mass email platforms shows.
Cold email: An unsolicited outreach message sent to someone with no prior relationship, common in B2B sales and subject to strict compliance rules.
Deployment: The act of sending a finished email campaign.
Email client: The application used to read email, such as Gmail, Outlook, or Apple Mail.
Webmail: Email accessed through a browser rather than a desktop app, such as Gmail or Yahoo Mail.
Landing page: A standalone web page an email links to, built to convert clicks into a specific action.
Mailbox provider (inbox service provider, ISP): The company that hosts recipient inboxes and filters incoming mail, such as Gmail, Yahoo, or Microsoft. The email industry often calls these ISPs, but that is loose usage. An internet service provider sells connectivity, and the two are no longer the same companies.
Email Metrics and Performance Terms
These terms measure how a campaign performed and where it succeeded or failed.
Open rate: The percentage of delivered emails recorded as opened, measured by a loaded tracking pixel. Privacy features that preload images now inflate the figure, so treat it as directional. Use it to compare your own campaigns over time, not to benchmark against published industry averages.
Unique opens: The number of individual recipients who opened an email at least once, ignoring repeat opens.
Click-through rate (CTR): The percentage of delivered emails that received at least one link click.
Click-to-open rate (CTOR): The percentage of openers who clicked, which isolates content and CTA effectiveness from subject line performance.
Conversion rate: The percentage of recipients who completed the campaign goal, such as a purchase or signup, after clicking.
Bounce rate: The percentage of sent emails that could not be delivered.
Hard bounce: A permanent delivery failure, usually from an invalid or nonexistent address. Remove these immediately.
Soft bounce: A temporary delivery failure, such as a full mailbox or a briefly unavailable server.
Unsubscribe rate: The percentage of recipients who opted out after receiving a campaign.
Spam complaint rate: The percentage of recipients who marked an email as spam. Google requires bulk senders to stay below 0.3 percent and advises targeting 0.1 percent, since sustained rates between those two figures still degrade inbox placement.
Delivery rate: The percentage of sent emails that receiving servers accept rather than bounce. A high delivery rate confirms acceptance only. It says nothing about whether the message reached the inbox or the spam folder.
Inbox placement rate: The percentage of delivered emails that reach the primary inbox rather than spam or a secondary tab. This is the figure that determines commercial outcomes, and it is the one most platform dashboards do not report by default.
Engagement rate: A measure of how recipients interact through opens, clicks, replies, and forwards. Mailbox providers use engagement to judge sender reputation.
List churn: The rate at which subscribers leave a list through unsubscribes, bounces, and complaints.
Return on investment (ROI): The revenue generated for each dollar spent on email marketing.
Revenue per email (RPE): The average revenue earned per email sent or per subscriber, used to measure monetization efficiency.
Cost per thousand (CPM): The price an advertiser pays for one thousand ad impressions, the standard unit for buying newsletter sponsorship inventory.
Effective cost per thousand (eCPM): Total revenue divided by impressions, multiplied by one thousand. It normalises earnings from different deal types, such as flat sponsorships and performance deals, into one comparable rate so publishers can see which inventory actually earns.
Cost per click (CPC): The amount paid for each click on an ad or link, used when advertisers pay for traffic rather than exposure.
Cost per acquisition (CPA): The amount paid for each completed action, such as a signup or purchase. CPA is the strictest performance model because payment depends on the outcome, not the click.
List and Subscriber Management Terms
These terms cover how you grow, organize, and maintain the people you email.
Email list: The database of contacts a sender emails.
Opt-in: The action of agreeing to receive email from a sender.
Opt-out: The action of withdrawing consent, usually through an unsubscribe link.
Single opt-in: Adding a subscriber immediately after signup without a confirmation step.
Double opt-in: Requiring subscribers to confirm through a follow-up email before they are added, which improves list quality.
Segmentation (list segmentation): Dividing a list into smaller groups based on behavior, demographics, purchase history, or interests so each group receives relevant email. Segmentation is also a deliverability tool, because sending only to engaged subgroups raises aggregate engagement signals and protects sender reputation.
Suppression list: A set of addresses permanently excluded from sending, typically unsubscribes, hard bounces, and spam complainers. Suppression operates above your active lists, so an address on it stays unmailed even if it is re-imported. This is what prevents an accidental send to someone who already opted out.
List hygiene: The ongoing removal of invalid, bouncing, and unengaged addresses to protect deliverability. See Emercury’s guide to email list hygiene for a maintenance routine.
List building: The process of growing a subscriber list through signup forms, lead magnets, and other opt-in methods.
List growth rate: The net rate at which a list gains subscribers after accounting for losses.
List fatigue (email fatigue): Declining engagement caused by sending too often or without relevance.
Signup form: A web form that collects email addresses and consent to join a list.
Preference center: A page where subscribers manage frequency, topics, and personal data.
Re-engagement (win-back) campaign: A series aimed at reactivating inactive subscribers before suppressing them.
Sunset policy: A rule that automatically suppresses subscribers who stay inactive for a defined period.
Graymail: Mail a recipient opted into but rarely engages with, which can drift toward the spam folder.
Lead: A potential customer who has shown interest, often by joining a list.
Lead nurturing: Guiding leads toward a purchase through a planned sequence of relevant emails.
Rented list (list rental): Paying to send to a third party’s list. It carries high deliverability and compliance risk and is discouraged.
Role-based address: A shared address tied to a function rather than a person, such as info@ or support@. These are often removed during hygiene.
Catch-all address: A domain setting that accepts mail to any address at that domain, which can mask invalid recipients.
Disposable email address: A temporary address used to avoid ongoing contact, common in low-quality or fake signups.
Email Campaign and Automation Terms
These terms describe how email is triggered, sequenced, tested, and tailored.
Marketing automation: Software that sends email based on rules, triggers, and schedules rather than manual sends.
Autoresponder: An automated email or sequence sent after a specific trigger, such as a signup.
Drip campaign: A series of pre-written emails sent on a fixed schedule or cadence.
Trigger (triggered email): An email sent automatically when a recipient takes a defined action.
Behavioral email: Email triggered by a subscriber’s behavior, such as browsing a page or making a purchase.
Welcome series: The first automated emails new subscribers receive to set expectations and build early engagement.
Abandoned cart email: A triggered message reminding shoppers of items left in an online cart.
Nurture sequence: A planned series that educates and builds trust before a sales ask.
Onboarding email: Email that helps new users or customers get started with a product or service.
Customer journey: The full path a contact takes from first touch to conversion and retention, often mapped inside automation.
Workflow (automated workflow): A visual or rule-based sequence of automated steps and conditions.
A/B test (split test): Sending two versions of an email to compare performance on a single variable, such as subject line.
Multivariate testing: Testing several variables at once to find the best-performing combination.
Personalization: Inserting subscriber-specific details, such as a first name or product recommendation, into an email.
Dynamic content: Content blocks that change based on subscriber data or segment.
Merge tag (mail merge): A placeholder that pulls in personalized data, such as a first name, at send time.
Progressive profiling: Gradually collecting subscriber data over time rather than all at once.
Tag: A label applied to contacts to organize them by interest, behavior, or source.
Email Design and Content Terms
These terms cover how an email is built and how it renders across inboxes.
Email template: A reusable layout that keeps branding and structure consistent across campaigns.
Drag-and-drop editor: A visual builder that lets users design emails without writing code.
WYSIWYG editor: A what-you-see-is-what-you-get editor that shows the final layout while you edit.
Responsive design: Email design that adapts to screen size for readability on mobile and desktop.
Plain text email: An email with no HTML formatting, images, or styling.
HTML email: An email built with HTML and CSS to include images, color, and layout.
Alt text: Text that describes an image, shown when images are blocked and read aloud by screen readers.
Dark mode: An inbox display setting that inverts colors, which can change how an email renders.
Image blocking: When an email client hides images by default until the recipient chooses to load them.
Interactive email (AMP email): Email that lets recipients take action inside the message, such as completing a form or browsing a carousel.
Preview pane: The inbox panel that shows part of an email before it is opened.
Text-to-image ratio: The balance of text to images in an email, which affects rendering and spam filtering.
Modular design: Building emails from reusable content blocks that can be rearranged for different campaigns.
Email Deliverability Terms
These terms determine whether your email reaches the inbox. For the bigger picture, see what email deliverability really means.
Deliverability: The ability of email to reach the inbox rather than spam or an outright block. It is the product of authentication, sender reputation, list quality, and content, not a setting a platform can switch on. Two senders on identical infrastructure can see very different results.
Sender reputation: A score mailbox providers assign to a sending domain and IP based on sending history, complaint rates, bounce rates, and subscriber engagement. Reputation is earned slowly and lost quickly, and it follows the sending domain even if you switch platforms. See our review of the tools that monitor sender reputation.
Sender score: A reputation metric, often on a 0 to 100 scale, that estimates the trustworthiness of a sending IP.
IP address: The numeric address of the server sending your email, tied directly to sender reputation.
Dedicated IP: A sending IP used by one sender, giving full control over reputation and full exposure to your own mistakes. Dedicated IPs need consistent volume to stay warm, so low-volume senders usually get better placement on a well-managed shared pool.
Shared IP: A sending IP used by multiple senders, where reputation is pooled.
IP warming: Gradually increasing send volume from a new IP so mailbox providers can build trust in it. A warm-up starts with your most engaged subscribers at low volume and scales over days or weeks. Skipping it makes a new IP look like a spam source.
Feedback loop (FBL): A service through which mailbox providers report spam complaints back to the sender.
Spam trap: An address operated by mailbox providers or blocklist operators to catch senders with poor list hygiene. Pristine traps never opted in and indicate purchased or harvested data. Recycled traps are abandoned real addresses and indicate you are not sunsetting inactive contacts.
Honeypot: A hidden field or address designed to catch bots and spammers.
Blocklist (blacklist): A database of IPs or domains flagged for spam that receiving servers consult before accepting mail. A listing with a major operator such as Spamhaus can halt delivery entirely, and delisting normally requires fixing the underlying sending problem before the request is granted.
Allowlist (whitelist): A list of trusted senders approved to reach the inbox.
Greylisting: A filter that temporarily rejects unknown senders, expecting legitimate servers to retry.
Throttling: Limiting send speed to a mailbox provider to avoid triggering rate limits.
Seed list: A set of test inboxes used to check inbox placement and rendering during a send.
Email verification (validation): Checking that an address is valid and deliverable before sending.
Spam filter: Software that scores and filters inbound email to block unwanted messages.
Spam score: A rating that estimates how likely an email is to be filtered as spam.
False positive: A legitimate email wrongly flagged as spam.
Bounce: Any failed delivery, categorized as hard or soft.
Deferral: A temporary delay when a mailbox provider asks the sender to retry later.
Postmaster: The role or tools responsible for a mail server’s reputation and deliverability, such as Google Postmaster Tools.
Bulk sender requirements: Rules from Gmail, Yahoo, and Microsoft for senders above volume thresholds, covering authentication, unsubscribe, and spam complaint rates. Gmail and Yahoo introduced theirs in February 2024, Microsoft followed in May 2025, and Gmail moved to hard enforcement with SMTP-level rejections in November 2025.
Email Authentication and Security Terms
These terms verify your identity as a sender and protect your domain from abuse.
Email authentication: The set of protocols that verify a sender’s identity to prevent spoofing and improve deliverability. Since February 2024, Gmail and Yahoo have required bulk senders to implement SPF, DKIM, and DMARC. Authentication is no longer optional hygiene, because non-compliant mail now faces rejection rather than spam filtering.
SPF (Sender Policy Framework): A DNS record listing the servers authorized to send email for a domain. Receiving servers check the sending IP against that list. SPF alone is weak, because it validates the envelope sender rather than the visible From address, which is why DMARC alignment matters.
DKIM (DomainKeys Identified Mail): A cryptographic signature added to outgoing mail, verified against a public key in the sender’s DNS. It proves the message was not altered in transit and genuinely originated from the signing domain. Unlike SPF, DKIM survives forwarding.
DMARC: A DNS policy that tells receiving servers how to handle mail failing SPF or DKIM, with three settings: none for monitoring, quarantine for spam routing, and reject for outright refusal. It also returns aggregate reports showing who is sending as your domain. A free DMARC record generator can help you create the record.
BIMI (Brand Indicators for Message Identification): A standard that displays a verified brand logo in the inbox for authenticated senders.
MX record: A DNS record that directs email to the correct mail servers for a domain.
DNS: The Domain Name System that maps domain names to servers and holds authentication records.
PTR record (reverse DNS): A record mapping an IP back to a hostname, required by some mailbox providers.
TLS: Transport Layer Security, the encryption that protects email in transit between servers.
Email spoofing: Forging a sender address to impersonate a trusted domain.
Phishing: Fraudulent email that tricks recipients into sharing sensitive information.
Quarantine: A DMARC policy action that routes failing mail to the spam folder rather than rejecting it.
One-click unsubscribe: A required mechanism that lets recipients opt out in a single action, mandated for bulk marketing mail.
List-Unsubscribe header: The email header that enables one-click unsubscribe in supporting inboxes.
Email Privacy and Compliance Terms
These terms cover the consent, disclosure, and data rules that govern email.
CAN-SPAM Act: The US law for commercial email, requiring accurate headers, honest subject lines, a physical postal address, and a working opt-out. The FTC compliance guide details each rule and its penalties.
GDPR: The European Union’s General Data Protection Regulation, which requires a lawful basis such as consent to process personal data and grants strong rights over that data.
CCPA: The California Consumer Privacy Act, which gives California residents rights over their personal data, including the right to opt out of its sale.
CASL: Canada’s Anti-Spam Legislation, which generally requires express or implied consent before sending commercial email to Canadian recipients.
Consent (express and implied): Permission to email someone. Express consent is a clear opt-in, while implied consent arises from an existing relationship under some laws.
Unsubscribe link: The link that lets recipients opt out of future email, required by law for commercial messages.
Apple Mail Privacy Protection (MPP): An Apple feature that preloads images and masks IP data, which inflates open rates and reduces their reliability.
Personally identifiable information (PII): Data that can identify an individual, such as name, email, or address, which privacy laws protect.
Permission-based sending: The practice of emailing only people who have granted consent, which underpins both compliance and deliverability.
Unsolicited commercial email (UCE): Commercial email sent without the recipient’s consent, commonly referred to as spam.
Technical and Infrastructure Terms
These terms describe the protocols and systems that move email and connect it to other tools.
SMTP (Simple Mail Transfer Protocol): The standard protocol used to send email between servers.
SMTP relay: A service that accepts outgoing mail and delivers it at scale on your behalf, handling authentication and throughput. See how SMTP relay differs from an ESP for when to use each.
API: An application programming interface, which lets software send email or exchange data with a platform programmatically. Most developer-focused providers offer both an API and SMTP credentials, as covered in our review of email delivery services for developers.
IMAP (Internet Message Access Protocol): A protocol for reading email stored on a server across multiple devices.
POP3 (Post Office Protocol): A protocol that downloads email from a server to a single device.
MTA (mail transfer agent): The server software that routes and delivers email between systems.
MDA (mail delivery agent): The component that delivers incoming mail to a recipient’s mailbox.
MUA (mail user agent): The email client a person uses to read and write messages.
MIME (Multipurpose Internet Mail Extensions): The standard that lets email carry formatting, images, and attachments.
CRM (customer relationship management): A system that stores the full customer record across sales, support, and marketing. See how an ESP differs from a CRM.
CDP (customer data platform): Software that unifies customer data from many sources into a single profile for targeting.
CDN (content delivery network): A network of servers that delivers images and assets quickly across regions.
MAP (marketing automation platform): A platform that manages automated, multi-channel marketing including email.
Email ad server: A system that inserts and tracks advertising inside newsletters and email inventory. Learn how email ad servers work.
Tracking pixel: A tiny invisible image that loads when an email is opened, used to record opens.
Webhook: An automated message sent from one system to another when an event occurs, such as a bounce or click.
Put This Email Marketing Terminology to Work
Email Platform Review tests and compares email marketing platforms, SMTP relays, and deliverability tools so you can see how these terms play out across real providers. Once the vocabulary is clear, the next step is matching the right features to your sending volume and goals. Start with our comparison of budget-friendly email marketing platforms if cost is the binding constraint, or our deliverability platform reviews if inbox placement is the problem you are actually solving.
Conclusion
Fluent email marketing terminology turns confusing reports into clear decisions. The metrics tell you what happened, the deliverability and authentication terms tell you why messages reach or miss the inbox, and the compliance terms keep your program legal and trusted. Bookmark this glossary, revisit the categories as your program grows, and use the precise terms when briefing teams or comparing platforms. Clear language leads to better email.
FAQs
1. What is email marketing terminology? Email marketing terminology is the set of terms, acronyms, and metrics used to plan, send, measure, and comply with email campaigns. It spans performance metrics like open rate and click-through rate, deliverability concepts like sender reputation and bounce, automation terms like drip campaign, authentication protocols like SPF and DKIM, and privacy laws like CAN-SPAM and GDPR.
2. What is the difference between delivery rate and deliverability? Delivery rate is the share of sent emails that receiving servers accept rather than bounce. Deliverability, or inbox placement, is the share of accepted emails that reach the primary inbox instead of spam. A campaign can have a high delivery rate but poor deliverability if most accepted messages land in the spam folder, so both numbers matter.
3. What is the difference between a hard bounce and a soft bounce? A hard bounce is a permanent delivery failure, usually from an invalid, closed, or nonexistent address. A soft bounce is a temporary failure, such as a full mailbox, a message that is too large, or a server that is briefly unavailable. Remove hard bounces immediately, and monitor repeated soft bounces before suppressing those addresses.
4. What does open rate actually measure now? Open rate is the percentage of delivered emails recorded as opened, based on a loaded tracking pixel. Privacy features such as Apple Mail Privacy Protection preload images and inflate opens, so the metric is now less reliable on its own. Marketers increasingly pair it with click-through rate and click-to-open rate for a truer read on engagement.
5. What is the difference between single opt-in and double opt-in? Single opt-in adds a subscriber to your list immediately after they submit a signup form. Double opt-in sends a confirmation email first and only adds the subscriber after they click the link inside it. Double opt-in produces a cleaner, more engaged list and fewer spam traps, while single opt-in grows lists faster but with more risk.
6. What are the Gmail and Yahoo bulk sender requirements? Since February 2024, senders of 5,000 or more messages per day to Gmail accounts must set up SPF, DKIM, and DMARC, offer one-click unsubscribe on marketing mail, and keep spam complaint rates below 0.3 percent. Yahoo introduced matching rules, and Microsoft began enforcing its own in May 2025. Gmail moved to hard enforcement with message rejections in November 2025.
7. What is the difference between SPF, DKIM, and DMARC? SPF is a DNS record listing which servers may send email for your domain. DKIM adds a cryptographic signature proving a message was not altered in transit. DMARC is a policy that tells receiving servers how to handle mail that fails SPF or DKIM, and it sends reports. The three work together to authenticate email and reduce spoofing.
8. What is a spam trap and why does it hurt deliverability? A spam trap is an email address used by mailbox providers and blocklist operators to catch senders with poor list hygiene. Pristine traps never opted in, and recycled traps are old abandoned addresses. Sending to either signals that you are not maintaining permission or removing inactive contacts, which can damage sender reputation and trigger blocklisting.
9. What is the difference between a dedicated IP and a shared IP? A dedicated IP is a sending address used by one sender, giving full control over reputation but requiring consistent volume and warm-up. A shared IP is used by multiple senders, so reputation is pooled and one sender’s behavior can affect others. High-volume, consistent senders often prefer dedicated IPs, while smaller senders benefit from a well-managed shared pool.
10. What is the difference between an ESP and a CRM? An email service provider stores lists, builds campaigns, sends email, and reports on results. A customer relationship management system stores the full customer record across sales, support, and marketing. Some platforms combine both, but an ESP is built around sending and measuring email, while a CRM is built around managing relationships and pipeline data.
11. What is IP warming? IP warming is the process of gradually increasing sending volume from a new IP address so mailbox providers can build trust in it. Sending high volume from a cold IP looks suspicious and can trigger filtering. A warm-up schedule starts with your most engaged subscribers and small volumes, then increases over days or weeks toward full capacity.
12. What is the difference between segmentation and personalization? Segmentation divides a list into smaller groups based on behavior, demographics, or interests so you can send more relevant campaigns. Personalization inserts subscriber-specific details, such as a first name or product recommendation, into an individual message. Segmentation decides who receives an email, while personalization tailors what each recipient sees inside it. The two are often used together.
13. What does CAN-SPAM require? The CAN-SPAM Act requires accurate header and from information, honest subject lines, a clear disclosure when a message is an advertisement, a valid physical postal address, and a working opt-out that is honored promptly. It applies to all commercial email, including business-to-business messages, and each violating email can carry significant civil penalties enforced by the FTC.
14. What is a suppression list? A suppression list is a set of email addresses that a platform will never send to, even if they appear in an active list. It typically holds unsubscribes, hard bounces, and spam complainers. Suppression lists prevent accidental sends to people who opted out or damaged your reputation, which supports compliance and protects deliverability.
15. What is a transactional email? A transactional email is a message triggered by a specific user action, such as a password reset, order receipt, shipping notice, or account alert. It is expected by the recipient and tied to a transaction rather than a promotion. Transactional email usually sends through separate infrastructure and is largely exempt from marketing unsubscribe rules.
16. What is the difference between SMTP and an SMTP relay? SMTP, the Simple Mail Transfer Protocol, is the standard used to send email between servers. An SMTP relay is a service that accepts your outgoing mail and delivers it at scale on your behalf, handling authentication, reputation, and throughput. Applications and platforms use an SMTP relay to send high volumes of transactional or marketing email reliably.
