Email Glossary
Your comprehensive guide to email marketing, deliverability, and verification terminology.
A
A Record
A DNS record that maps a domain name to an IPv4 address.
DNSAbuse Complaint
When a recipient marks an email as spam or junk, generating a complaint to the sender's email provider.
DeliverabilityAccept-All Domain
See Catch-All Domain. A mail server configured to accept emails sent to any address at that domain.
VerificationB
Backscatter
Bounce messages sent to forged sender addresses, often caused by spam or viruses using fake return addresses.
DeliverabilityBlacklist
A database of IP addresses or domains identified as sources of spam. Also called blocklist or DNSBL.
DeliverabilityBlocklist
See Blacklist. A list of IPs or domains blocked due to spam or malicious activity.
DeliverabilityBounce
An email that cannot be delivered and is returned to the sender with an error message.
DeliverabilityBounce Rate
The percentage of sent emails that could not be delivered. Calculated as (bounced emails / sent emails) × 100.
MetricsC
CAN-SPAM Act
US law establishing requirements for commercial email, including opt-out mechanisms and sender identification.
ComplianceCatch-All Domain
A mail server configured to accept emails to any address at the domain, making individual mailbox verification impossible.
VerificationClick-Through Rate (CTR)
The percentage of email recipients who clicked on one or more links in an email.
MetricsCold Email
An unsolicited email sent to a recipient without prior contact or relationship.
Email MarketingComplaint Rate
The percentage of recipients who mark your email as spam. Should be kept below 0.1%.
MetricsD
Dedicated IP
An IP address used exclusively by one sender, giving full control over sender reputation.
InfrastructureDeliverability
The ability of an email to reach the recipient's inbox rather than being blocked or filtered to spam.
DeliverabilityDisposable Email
A temporary email address created for short-term use, often to avoid spam or hide identity.
VerificationDKIM
DomainKeys Identified Mail. An email authentication method using cryptographic signatures to verify sender identity.
AuthenticationDMARC
Domain-based Message Authentication, Reporting & Conformance. A policy framework building on SPF and DKIM.
AuthenticationDNS
Domain Name System. The internet's phone book that translates domain names to IP addresses.
DNSDNSBL
DNS-based Blackhole List. A blacklist queryable via DNS to check if an IP is flagged for spam.
DeliverabilityDomain Reputation
A score assigned to a sending domain based on email engagement, complaints, and sending practices.
DeliverabilityDouble Opt-In
A subscription process requiring users to confirm their email address by clicking a verification link.
ComplianceE
Email Authentication
Technical methods (SPF, DKIM, DMARC) to verify that an email comes from its claimed sender.
AuthenticationEmail Client
Software used to read, send, and manage emails (e.g., Gmail, Outlook, Apple Mail).
GeneralEmail Header
Metadata at the top of an email containing routing information, sender details, and authentication results.
GeneralEmail Hygiene
The practice of maintaining a clean email list by removing invalid, inactive, and risky addresses.
VerificationEmail Service Provider (ESP)
A company that provides email marketing and sending services (e.g., Mailchimp, SendGrid, Klaviyo).
InfrastructureEmail Verification
The process of validating that an email address exists, is properly formatted, and can receive messages.
VerificationEmail Warmup
Gradually increasing email sending volume on a new IP or domain to build sender reputation.
DeliverabilityEngagement Rate
A metric measuring how recipients interact with emails through opens, clicks, and replies.
MetricsEnvelope Sender
The email address used in the SMTP conversation, which may differ from the visible "From" address.
GeneralF
G
GDPR
General Data Protection Regulation. EU law governing data privacy and consent for email marketing.
ComplianceGraymail
Legitimate email that recipients signed up for but no longer engage with, often filtered or ignored.
DeliverabilityGreylisting
An anti-spam technique that temporarily rejects emails from unknown senders, expecting legitimate servers to retry.
DeliverabilityH
Hard Bounce
A permanent delivery failure, typically because the email address doesn't exist or the domain is invalid.
DeliverabilityHeader
See Email Header. The metadata portion of an email containing routing and authentication information.
GeneralHoneypot
A type of spam trap - an email address created specifically to catch spammers harvesting addresses.
DeliverabilityI
IMAP
Internet Message Access Protocol. A protocol for retrieving emails from a server while keeping them stored remotely.
InfrastructureInbox Placement
Whether an email lands in the primary inbox, promotions tab, or spam folder.
DeliverabilityIP Reputation
A score assigned to an IP address based on its email sending history and recipient engagement.
DeliverabilityIP Warmup
The process of gradually increasing sending volume from a new IP address to establish reputation.
DeliverabilityISP
Internet Service Provider. In email context, often refers to mailbox providers like Gmail, Yahoo, and Microsoft.
InfrastructureM
Mail Transfer Agent (MTA)
Software that transfers emails between servers using SMTP protocol.
InfrastructureMailbox Provider
A service that hosts email accounts and manages inbox delivery (e.g., Gmail, Outlook, Yahoo).
InfrastructureMIME
Multipurpose Internet Mail Extensions. A standard for formatting non-text email content like attachments and HTML.
GeneralMX Record
Mail Exchange record. A DNS record specifying the mail server responsible for receiving email for a domain.
DNSO
Open Rate
The percentage of delivered emails that were opened by recipients.
MetricsOpt-In
When a user gives explicit permission to receive emails, typically by subscribing to a list.
ComplianceOpt-Out
When a user withdraws permission to receive emails, typically by clicking an unsubscribe link.
ComplianceP
Phishing
Fraudulent emails designed to trick recipients into revealing sensitive information or clicking malicious links.
SecurityPOP3
Post Office Protocol version 3. A protocol for downloading emails from a server to a local device.
InfrastructurePristine Spam Trap
An email address that was never used for legitimate purposes, created solely to catch spammers.
DeliverabilityR
Recycled Spam Trap
A previously valid email address repurposed as a spam trap after being abandoned for an extended period.
DeliverabilityReturn Path
The email address where bounce notifications are sent. Used in SPF authentication.
GeneralRole-Based Email
An email address associated with a function rather than a person (e.g., info@, support@, sales@).
VerificationS
Sender Policy Framework
See SPF. An email authentication protocol that specifies which servers can send email for a domain.
AuthenticationSender Reputation
A score reflecting the trustworthiness of an email sender based on sending practices and engagement.
DeliverabilitySender Score
A reputation rating from 0-100 assigned to sending IP addresses, provided by Validity (formerly Return Path).
DeliverabilityShared IP
An IP address used by multiple senders, where reputation is influenced by all users' behavior.
InfrastructureSingle Opt-In
A subscription process where users are added to a list immediately after submitting their email, without confirmation.
ComplianceSMTP
Simple Mail Transfer Protocol. The standard protocol for sending emails between servers.
InfrastructureSoft Bounce
A temporary delivery failure, often due to a full mailbox, server issues, or message size limits.
DeliverabilitySpam
Unsolicited bulk email, typically commercial in nature, sent without recipient consent.
GeneralSpam Filter
Software that analyzes emails to identify and block spam from reaching the inbox.
DeliverabilitySpam Trap
An email address used to identify spammers. Includes pristine traps, recycled traps, and typo traps.
DeliverabilitySPF
Sender Policy Framework. A DNS-based email authentication method listing authorized sending servers for a domain.
AuthenticationSpoofing
Forging email headers to make a message appear to come from a different sender than the actual source.
SecuritySunsetting
The practice of removing unengaged subscribers from email lists to maintain list quality and sender reputation.
Email MarketingSyntax Validation
Checking if an email address follows the correct format (e.g., user@domain.com) according to RFC standards.
VerificationT
Throttling
Rate limiting email sending speed to avoid overwhelming receiving servers or triggering spam filters.
DeliverabilityTLS
Transport Layer Security. Encryption protocol securing email transmission between servers.
SecurityTransactional Email
Automated emails triggered by user actions (e.g., order confirmations, password resets, notifications).
Email MarketingTypo Trap
A spam trap based on common misspellings of popular domains (e.g., gmial.com instead of gmail.com).
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