Every email term you'll meet, explained in plain English.
From SPF to BIMI, spam traps to warmup. Search by name, category, or phrase - answers are short, sourced, and actionable.
A
3 termsARC (Authenticated Received Chain)
A protocol that preserves email authentication results across forwarding hops, allowing downstream receivers to validate the original authentication.
Authentication (Email)
The process of verifying that an email was actually sent by the domain it claims to be from, using protocols like SPF, DKIM, and DMARC.
A Record
A DNS record that maps a domain name to an IPv4 address. Used in email infrastructure to resolve hostnames to IPs.
B
6 termsBlacklist (Email)
A real-time database of IP addresses or domains known to send spam. Being listed can severely impact email deliverability.
BIMI (Brand Indicators for Message Identification)
A standard that allows senders to display their brand logo next to authenticated emails in supporting mailbox providers.
Bounce (Hard)
A permanent email delivery failure caused by an invalid, non-existent, or blocked recipient address.
Bounce (Soft)
A temporary email delivery failure caused by a full mailbox, server downtime, or message size limits.
Bounce Rate
The percentage of sent emails that could not be delivered. A high bounce rate damages sender reputation.
Bulk Sender
An entity that sends large volumes of email. Google and Yahoo define bulk senders as those sending 5,000+ messages per day.
C
3 termsCAN-SPAM Act
A U.S. law that sets rules for commercial email, including requirements for opt-out mechanisms and truthful headers.
Complaint Rate
The percentage of recipients who mark your email as spam. Google requires bulk senders to stay below 0.3%.
Content Filtering
The process by which mailbox providers analyze email content to determine if it is spam or legitimate.
D
8 termsDedicated IP
An IP address used exclusively by one sender. Your reputation is entirely your own, unlike shared IPs.
Deliverability
The ability of an email to reach the recipient's inbox rather than being filtered to spam or rejected.
DKIM (DomainKeys Identified Mail)
An email authentication method that uses cryptographic signatures to verify that an email was authorized by the domain owner.
DMARC
An email authentication protocol that builds on SPF and DKIM to give domain owners control over how unauthenticated email is handled.
DNS (Domain Name System)
The internet's directory system that translates domain names into IP addresses. Critical for SPF, DKIM, DMARC, and MX records.
DNSBL (DNS-based Blackhole List)
A blacklist queried via DNS. Mail servers check incoming connections against DNSBLs to identify known spam sources.
Domain Reputation
A score assigned by mailbox providers to a sending domain based on its email sending practices and authentication.
Double Opt-in
A signup process where subscribers must confirm their email address by clicking a verification link after subscribing.
E
5 termsEmail Authentication
The collective term for SPF, DKIM, and DMARC protocols that verify email sender identity.
Email Header
Metadata included with every email containing routing information, authentication results, and technical details.
Engagement (Email)
How recipients interact with your emails - opens, clicks, replies, forwards. High engagement improves sender reputation.
ESP (Email Service Provider)
A company that provides email sending infrastructure, such as SendGrid, Mailchimp, or Amazon SES.
Envelope Sender
The email address used in the SMTP MAIL FROM command. Used for bounce handling and SPF checks.
F
2 termsG
3 termsGDPR
An EU regulation governing personal data protection that impacts email marketing through consent requirements.
Google Postmaster Tools
A free Google service that provides senders with data on domain reputation, spam rates, and authentication.
Graylisting
An anti-spam technique where a mail server temporarily rejects email from unknown senders.
I
3 termsInbox Placement
Whether an email lands in the primary inbox rather than spam, promotions tab, or being rejected.
IP Reputation
A score assigned to an IP address based on the quality and volume of email sent from it.
IP Warmup
The process of gradually increasing email volume from a new IP to build positive sending reputation.
L
2 termsM
3 termsMail Transfer Agent (MTA)
Software that routes and delivers email between servers using SMTP. Examples: Postfix, Sendmail.
Mailbox Provider
A service hosting email accounts and managing incoming mail delivery. Examples: Gmail, Outlook, Yahoo Mail.
MX Record
A DNS record specifying which mail servers accept email for a domain, along with priority values.
O
2 termsP
3 termsPhishing
Email fraud where attackers impersonate legitimate senders to steal credentials or install malware.
Pristine Spam Trap
An email address never used by a real person, created specifically to catch spammers.
PTR Record
A DNS record that maps an IP address back to a hostname (reverse DNS). Required for proper mail server config.
R
4 termsrDNS (Reverse DNS)
Resolving an IP address to a hostname using PTR records. Essential for email deliverability.
Recycled Spam Trap
A previously valid email address abandoned and repurposed as a spam trap. Indicates poor list hygiene.
Reject (DMARC)
The strictest DMARC policy (p=reject) that tells receivers to block unauthenticated email entirely.
Return-Path
The email address where bounce messages are sent. Set during SMTP and used for SPF alignment.
S
10 termsSender Reputation
An overall assessment of a sender's trustworthiness based on email practices, authentication, and engagement.
Sender Reputation Score
SenderReputation.org's proprietary A-F grading system evaluating authentication, blacklists, DNS, and infrastructure.
Shared IP
An IP address used by multiple email senders. Your reputation is affected by all senders sharing the IP.
SMTP (Simple Mail Transfer Protocol)
The standard protocol for sending email between servers.
Spam Complaint
When a recipient marks an email as spam. Each complaint damages sender reputation.
Spam Filter
Software analyzing incoming email to identify and block unwanted or malicious messages.
Spam Trap
An email address used to identify spammers. Types include pristine traps and recycled traps.
SPF (Sender Policy Framework)
An email authentication protocol specifying which IP addresses are authorized to send email for a domain.
STARTTLS
An SMTP extension that upgrades a plain-text connection to encrypted TLS. Essential for email privacy.
Suppression List
A list of email addresses that should not receive email, including unsubscribes and hard bounces.
T
3 termsThrottling
When a receiving server limits the rate of incoming email from a sender due to volume or reputation concerns.
TLS (Transport Layer Security)
An encryption protocol securing email in transit between servers. Prevents eavesdropping.
Transactional Email
Email triggered by a user action - password resets, order confirmations, account notifications.