A
Alignment (SPF/DKIM)
When the domain in the "From" header matches the domain used in SPF and/or DKIM authentication.
API (Application Programming Interface)
In email, it’s a way for your application to "talk" to an ESP to trigger transactional emails.
B
BIMI (Brand Indicators for Message Identification)
A standard that allows companies to display their brand logo next to their emails in the inbox.
Blacklist (Blocklist)
A real-time database that identifies IP addresses or domains suspected of sending spam.
C
CAN-SPAM Act
A U.S. law that sets rules for commercial email and gives recipients the right to have you stop emailing them.
CASL (Canada’s Anti-Spam Legislation)
One of the world's strictest anti-spam laws, requiring "express consent" in most cases.
CNAME Record
A type of DNS record that maps one domain name to another, often used for custom tracking domains.
Complaint Rate
The percentage of recipients who mark an email as "Spam."
D
Dedicated IP
An IP address used exclusively by a single sender, giving them total control over their reputation.
Deferral (Throttling)
When a mailbox provider temporarily rejects an email, often telling the sender to "try again later."
DKIM (DomainKeys Identified Mail)
When a mailbox provider temporarily rejects an email, often telling the sender to "try again later."
DMARC (Domain-based Message Authentication, Reporting, and Conformance)
A protocol that uses SPF and DKIM to tell servers how to handle emails that fail authentication.
DNS (Domain Name System)
The "phonebook" of the internet that translates domain names into IP addresses.
Domain Reputation
The "health" and trustworthiness of your specific domain name across various IP addresses.
Double Opt-In
A process where a user signs up for a list and must click a confirmation link in an email to verify their intent.
E
Engagement Rate
A metric calculating how users interact with your emails (opens, clicks, replies).
ESP (Email Service Provider)
A platform (like Klaviyo or Mailchimp) used to send email marketing campaigns.
F
Feedback Loop (FBL)
A service where ISPs notify a sender when a recipient marks their email as spam.
G
GDPR (General Data Protection Regulation)
A rigorous EU data privacy law regarding how you collect and store email addresses.
Google Postmaster Tools
A free tool to track domain reputation, spam rates, and encryption status specifically for Gmail.
Greylisting
A technique where receiving servers temporarily "reject" an email from an unknown sender to test if it's a legitimate server.
H
Hard Bounce
A permanent delivery failure (e.g., the email address is invalid).
Header
The "hidden" data at the top of an email containing routing info, authentication results, and sender details.
Honeypot
A type of spam trap hidden in a website's code to catch automated bots scraping email addresses.
I
Inbox Placement
The percentage of sent emails that successfully reach the primary inbox rather than the spam folder.
IP Reputation
A score based on the sending history of a specific IP address.
J
K
L
List Wash/Cleaning
The process of removing inactive, invalid, or "dead" email addresses from a mailing list.
List-Unsubscribe Header
Code that allows mailbox providers to display an "Unsubscribe" button at the top of the email interface.
M
Marketing Email
Commercial emails sent to a group of people containing promotions or newsletters.
MIME (Multipurpose Internet Mail Extensions)
A standard that allows email to support non-ASCII text and attachments.
MTA (Mail Transfer Agent)
Software that transfers electronic mail messages from one computer to another.
N
Namespace
In DNS, the hierarchy and organization of domain names.
O
P
Phishing
A fraudulent attempt to obtain sensitive information by masquerading as a trustworthy entity.
Preheader
The short summary text that follows the subject line in an inbox preview.
PTR Record (Reverse DNS)
A record that maps an IP address back to a domain name to verify sender identity.
P
Q
R
S
Seed List
A record that maps an IP address back to a domain name to verify sender identity.
Shared IP
An IP address used by multiple senders; reputation is shared among all users.
SMTP (Simple Mail Transfer Protocol)
The standard protocol for sending and receiving email across the internet.
SNDS (Smart Network Data Service)
A service provided by Outlook.com to give senders data on their reputation.
Snowshoeing
A spamming technique where volume is spread across many IPs and domains to avoid detection.
Soft Bounce
A temporary delivery failure (e.g., the recipient's mailbox is full).
Spam Trap
An email address used by blacklists and ISPs to identify senders with poor list-building practices.
SPF (Sender Policy Framework)
A DNS record listing the IP addresses and domains authorized to send email for your domain.
Spoofing
Forgery of an email header to make a message appear to have originated from a source other than the actual one.
Sunset Policy
A strategy for automatically removing unengaged subscribers after a certain period of time.
T
TLS (Transport Layer Security
A protocol that encrypts email in transit to prevent tampering.
Transactional Email
Non-marketing emails triggered by a user's action (e.g., password resets).
U
V
VMC (Verified Mark Certificate)
A digital certificate required to display a logo via BIMI.