This glossary defines common email deliverability terms and concepts to help you better understand how email systems, infrastructure, and inbox providers work.
Why This Glossary Matters
Email deliverability involves technical concepts like authentication, domains, and reputation. Understanding the terms mentioned below helps you troubleshoot issues and improve inbox placement.
A
A Record
A DNS record that maps a domain to an IP address. It helps direct traffic to the correct server.
Allowlist
A list of approved domains or IPs that are allowed to send messages (also called a whitelist).
B
Blocklist
A database of domains or IPs flagged for sending spam. Being listed can harm deliverability.
Bounce
Occurs when an email cannot be delivered:
Hard bounce → permanent issue (invalid email)
Soft bounce → temporary issue (full inbox, server issue)
Branded Sending Domain
A domain owned by your business is used to send emails instead of a shared domain.
C
CAN-SPAM Act
A U.S. law that regulates commercial email and gives recipients the right to opt out.
CASL
Canada’s anti-spam law governs how businesses send electronic communications.
CCPA
A privacy law that regulates how businesses handle the personal data of California residents.
Click Tracking
A method used to track link clicks by routing users through a tracking URL.
CNAME Record
A DNS record that maps one domain name to another.
D
Dedicated IP Address
An IP address used exclusively by one sender.
Learn more: Dedicated vs. Shared IPs: What’s the Difference?
Deliverability
The likelihood that your email reaches the inbox (not spam).
Delivery
Whether your email was successfully accepted by the recipient’s server.
Learn more: Delivery vs. Deliverability Across Channels
DKIM (DomainKeys Identified Mail)
An authentication method that verifies your email hasn’t been altered.
DMARC
An authentication protocol that builds on SPF and DKIM to protect against spoofing.
DNS (Domain Name System)
The system that connects domain names to servers and verifies sender identity.
Domain Reputation
How inbox providers evaluate the trustworthiness of your domain.
E
Email Engagement
How recipients interact with your emails (opens, clicks, replies).
ESP (Email Service Provider)
A platform used to send marketing or transactional emails (e.g., Birdeye).
G
GDPR
A European law that regulates how personal data is collected and processed.
H
Hard Bounce
A permanent delivery failure due to invalid or non-existent email addresses.
Header (Email Header)
Technical information about an email, including sender, recipient, and authentication details.
I
Inbox Provider (Mailbox Provider)
Services like Gmail or Outlook that manage email delivery and filtering.
IP Address
A unique identifier for the server sending your emails.
IP Reputation
How inbox providers evaluate the trustworthiness of your sending IP.
L
List Cleaning
The process of removing invalid or unengaged contacts from your email list.
List Bombing
A malicious attack where large volumes of fake emails are added to a signup form.
M
MX Record
A DNS record that specifies which server handles incoming email for a domain.
P
Phishing
A fraudulent attempt to obtain sensitive information by impersonating a trusted sender.
Spam Trap
Email addresses used to identify senders with poor list practices.
R
Ramping (Warming)
The process of gradually increasing sending volume to build a positive reputation.
S
Sender Reputation
A measure of how trustworthy your emails appear to inbox providers.
Learn more: What is Sender Reputation and Why It Matters
Shared IP Address
An IP used by multiple senders.
Shared Sending Domain
A domain used by multiple accounts to send emails.
Spam Complaint
When a recipient marks your email as spam.
SPF (Sender Policy Framework)
An authentication method that verifies authorized sending sources.
Subdomain
A prefix added to your main domain (e.g., send.example.com).
Learn more: What is a Branded Sending Subdomain?
Suppress (Suppressed Contact)
A contact that can no longer receive emails due to unsubscribes, bounces, or complaints.
T
TXT Record
A DNS record used to store authentication data like SPF, DKIM, and DMARC.
W
Warming
The process of building a sender reputation for a new domain or IP by gradually increasing email volume.
Key Takeaway
Understanding these terms helps you better manage your email program, troubleshoot deliverability issues, and optimize performance. Strong deliverability comes from a combination of good infrastructure, clean data, and consistent sending practices.