Email Validation Glossary

Every industry has its own terms. We tried to create a glossary of email validation, email verification, and email marketing terms and explain each of them. Here you can find the full index of the terms.

A
A Record

A DNS record that maps a domain to an IPv4 address. Email systems use it to locate where messages should be delivered.

A/B Split

A testing method that compares two versions of an email to see which performs better.

Above the Fold

The part of an email visible without scrolling. Content here gets the most attention.

Abuse Emails

Emails reported as spam or harmful by recipients, damaging sender reputation.

Accept-All

A mail server setup that accepts all addresses on a domain, valid or not.

Account Suspended

Status indicating sending privileges are paused due to policy or compliance issues.

Account Under Review

A temporary restriction while sending activity is evaluated.

Address-by-Address Analysis

Validation that checks each email individually instead of bulk assumptions.

Affiliate

A partner who promotes products or services in exchange for commission.

Alias

An alternate email address that forwards messages to a main inbox.

Allowlist

A list of trusted senders allowed to bypass spam filters.

Application Programming Interface (API)

A system that allows applications to communicate programmatically.

Asynchronous Bounce

A bounce reported after initial email acceptance by the server.

Attachment

A file included with an email message.

Authentication

Verification of sender identity using SPF, DKIM, or DMARC.

B
BIMI

An email standard that displays verified brand logos in inboxes.

Blacklist

A database of IPs or domains blocked due to spam behavior.

Blast

A mass email sent to a large list at once.

Block

An action preventing emails from reaching a recipient.

Blocked

Status showing emails are being rejected by the receiving server.

Blocklist

A list used by mail servers to deny known spam sources.

Bounce

An email that could not be delivered.

Bounce Handling

How bounces are processed and categorised by mail systems.

Bounce Message

A notification explaining why delivery failed.

Bounce Rate

The percentage of emails that failed delivery.

Bulk Folder

An inbox folder for promotional or non-priority emails.

C
Call to Action (CTA)

An instruction prompting the recipient to take action.

CAN-SPAM

A US law regulating commercial email practices.

Canadian Anti-Spam Legislation (CASL)

Canada’s law governing electronic communications.

Canonical Name (CNAME)

A DNS record that aliases one domain name to another.

Catch-all Emails

Addresses that receive emails sent to any username on a domain.

Click

An interaction where a recipient clicks a link.

Click-Through Rate

Percentage of recipients who clicked a link.

Click-to-Open Rate

Clicks divided by opens, measuring engagement quality.

Cloudmark

A spam filtering system used by mailbox providers.

Co-Registration

Collecting email consent during another signup process.

Commercial Email

Email sent to promote products or services.

Complaint Rate

Percentage of users who report emails as spam.

Complaints

Spam reports submitted by recipients.

Compliance

Adherence to email laws and policies.

Confirmation Email

An email sent to verify a user action.

Confirmed Opt-In

A subscription method requiring explicit confirmation.

Content

The text, images, and links inside an email.

Conversion

A completed desired action such as a signup.

Conversion Rate

Percentage of recipients who converted.

CSV

A file format used to store and upload email lists.

D
De-Duplication

Removing duplicate email addresses from a list.

Dedicated IP Address

An IP used by a single sender only.

Deliverability

Ability of emails to reach the inbox.

Deliverability Rate

Percentage of emails successfully delivered.

Deliverable

An email address capable of receiving mail.

Delivered Email

An email accepted by the recipient’s server.

Delivery Rate

Delivered emails divided by sent emails.

Denial-of-Service Attack or List-Bomb Attack

An attack flooding inboxes with high email volume.

Disposable

Temporary email addresses used briefly.

Domain

The name identifying a website or email system.

Domain Name System (DNS)

System translating domain names into IP addresses.

DMARC

An authentication protocol protecting domains from spoofing.

DomainKeys

An early email authentication method.

DKIM

A cryptographic method proving message integrity.

Dynamic Content

Email content that changes based on user data.

E
Email Append

Adding email addresses to existing records.

Email Checker / Validator / Verifier

A tool that identifies invalid or risky email addresses.

Email Client

Software used to read and send emails.

Email Deliverability

Inbox placement success of sent emails.

Email Filter

A system that classifies incoming emails.

Email Prefix

The part before the @ symbol.

Email Service Provider (ESP)

A platform used to send and manage email campaigns.

Email Validation

Checking if an email is formatted and reachable.

Email Verification

Confirming an email address actually exists.

Engagement

User interaction with email content.

Everything List

An unsegmented email list.

Explicit Consent

Clear permission given to receive emails.

F
False Positive

A legitimate email incorrectly flagged as spam.

Feedback Loop (FBL)

Reports from ISPs when users mark emails as spam.

Footer

The bottom section of an email.

Friendly Form

A signup form designed to increase conversions.

G
GDPR

European regulation governing personal data use.

Google Postmaster Tools

A dashboard for monitoring Gmail delivery performance.

Graymail

Emails users receive but rarely engage with.

Greylisting

A technique that temporarily rejects unknown senders.

H
Hard Bounce

A permanent delivery failure due to invalid address.

Header

Metadata containing routing and authentication info.

Honeypot Spam Trap

An address used to detect spam activity.

I
Implicit Consent

Permission inferred from an existing business or customer relationship rather than explicit signup.

Inactive Subscriber

A subscriber who has not opened or clicked emails for a long period.

Infrastructure

The technical systems and servers used to send and receive emails.

Internet Service Provider (ISP)

A company that provides internet access and often operates mail servers.

IP Address

A numerical identifier assigned to a server for sending or receiving email.

IP Reputation

A trust score assigned to an IP based on its email sending behavior.

L
List

A collection of email addresses used for sending campaigns.

List Hygiene

The practice of removing invalid, inactive, or risky emails from a list.

List Rental

The practice of paying to send emails to another company’s list.

List-Unsubscribe

An email header that allows easy unsubscribing directly from the inbox.

M
Mail Bombing

An attack that floods inboxes or servers with massive volumes of email.

Mail Transfer Agent (MTA)

Software responsible for transferring emails between servers.

Mailbox Provider (MBP)

A company that provides email inbox services to users.

Merge Fields

Dynamic placeholders used to personalise email content.

Multi-Part MIME

An email format that allows multiple content types in one message.

Multipurpose Internet Mail Extension (MIME)

A standard that defines how different data types are transmitted via email.

MX (Mail exchanger) Record

A DNS record that specifies which server receives emails for a domain.

MX Lookup

The process of checking MX records for a domain.

O
Omnivore

An inbox user who receives and opens a wide range of email types.

Opt-In

The act of giving permission to receive emails.

Opt-Out / Unsubscribe

The action of stopping future email communications.

P
Panel Data

Email engagement data collected from a sample group of users.

Permission

User consent to receive email communication.

Phishing

Fraudulent emails designed to steal sensitive information.

Post Office Protocol (POP)

An email protocol used to retrieve messages from a server.

Postmaster

A role or system responsible for managing email delivery.

Preference Center

A page where subscribers manage email frequency and topics.

R
Re-Confirm Campaign

An email campaign asking subscribers to confirm continued interest.

Re-Engagement Campaign

A campaign designed to win back inactive subscribers.

Recycled Spam Traps

Old email addresses reused to identify poor list hygiene.

Reply-To Address

The email address that receives replies from recipients.

Reputation

A sender trust score based on engagement and complaints.

Return Path Address

An address used to receive bounce messages.

Reverse DNS

A method that maps an IP address back to a domain name.

Role-Based Emails

Addresses linked to roles like info@ or support@ rather than individuals.

S
Safe List

A list of approved senders allowed to reach the inbox.

Seeds

Test email addresses used to monitor inbox placement.

Segment

A subset of an email list grouped by shared attributes.

Segmentation

The process of dividing lists into targeted groups.

Sender Policy Framework (SPF)

An authentication method that defines authorised sending servers.

Server

A system that sends, receives, or stores email.

Shared IP

An IP address used by multiple senders.

Simple Mail Transfer Protocol (SMTP)

The protocol used to send emails between servers.

Smart Network Data Service (SNDS)

A Microsoft tool for monitoring IP reputation.

SMTP Bounce Codes

Standardised codes explaining email delivery failures.

Snowshoeing

A spam technique that spreads email volume across many IPs.

Soft Bounce

A temporary delivery failure such as a full inbox.

Spam

Unwanted or unsolicited email messages.

SORBS

A blocklist used to identify spam sources.

Spam Trap

An address used to detect unsolicited email.

SURBL

A blocklist focusing on spam related URLs.

SpamAssassin

A widely used spam filtering system.

SpamCop

A service that reports spam sources.

Spamhaus

An organisation that tracks spam and threat intelligence.

Spoofing

Forging sender identity to appear legitimate.

Stale List

An outdated list with inactive or invalid addresses.

Subscriber

A person who has opted in to receive emails.

Sunset Policy

A rule for removing inactive subscribers after a set period.

Suppression File

A list of addresses excluded from sending.

T
Tabs

Inbox categories that separate emails by type.

Throttling

Limiting email send speed to avoid server overload.

Toxic Domain

A domain associated with spam or malicious activity.

Transactional Email

Automated emails triggered by user actions.

U
UCEPROTECT

A DNS based blocklist tracking abusive IP ranges.

Unique Open Rate

The percentage of recipients who opened an email at least once.

Unsolicited Commercial Emails (UCE)

Commercial emails sent without recipient consent.

Unsubscribe

The process of opting out from email communications.

W
Warm Up

A gradual increase in email volume to build sender reputation.

Whitelist

A list of senders explicitly allowed into the inbox.

WHOIS

A public database showing domain ownership information.

X
X-header

A custom email header used for tracking or routing purposes.