📘 SelfMailKit Email Glossary
Clear definitions of technical and industry terms used in modern email infrastructure.
A–E
API (Application Programming Interface)
A set of tools that allows apps to communicate; used to send and manage emails programmatically.
AMP Email (Accelerated Mobile Pages)
Interactive emails that allow users to perform actions (like RSVPs) directly inside the email.
A/B Testing
Sending two email versions to test which performs better.
Authentication
The process of verifying sender identity (via SPF, DKIM, DMARC).
Attachment
A file included with an email message.
AWS SES (Amazon Simple Email Service)
A popular cloud email delivery platform used with SelfMailKit.
Blacklist
A list of domains or IPs flagged as spam senders by ISPs.
Blocklist
Another term for a blacklist - often maintained by third parties like Spamhaus.
Bounce
A returned email due to delivery failure (hard or soft).
Bulk Email
High-volume email, usually promotional or marketing in nature.
BYO (Bring Your Own)
Typically refers to using your own SES or infrastructure with a third-party tool like SelfMailKit.
Campaign
A coordinated series of emails sent to a list.
CAN-SPAM Act
U.S. law setting rules for commercial emails (e.g., requiring an unsubscribe link).
Click Rate
Percentage of recipients who clicked a link in your email.
Cold Email
Unsolicited email sent to a prospect (legal restrictions apply).
Compliance
Adherence to legal and technical email regulations (GDPR, CAN-SPAM, etc.).
Contact List
The list of recipients you're sending to.
Custom Domain
A domain you control and configure for branded sending.
CTA (Call to Action)
A prompt in an email encouraging the user to take action.
DKIM (DomainKeys Identified Mail)
Cryptographic authentication that ensures message integrity.
DMARC
A policy that builds on SPF and DKIM to prevent domain spoofing.
DNS (Domain Name System)
Internet system that resolves domains, used in email auth setup.
Domain Reputation
A measurement of a domain's trustworthiness used by spam filters.
Double Opt-In
A two-step signup process for confirming subscriptions.
Drip Campaign
A series of automated, time-triggered emails.
F–M
Footer
The bottom section of an email, often containing unsubscribe links and legal text.
From Address
The sender address visible to recipients.
Hard Bounce
A permanent delivery failure.
Header
Metadata of an email (e.g., from, to, subject, etc.).
HTML Email
Email that includes images, styles, and layout using HTML code.
Inbox Placement
The ability of an email to land in the inbox vs. spam folder.
IP Address
Internet Protocol address of the sending server.
IP Reputation
Trust score assigned to a sending IP by ISPs.
IP Warming
Gradual increase of sending volume from a new IP to build trust.
List Hygiene
The process of keeping email lists clean and up-to-date.
List Segmentation
Dividing your audience into targeted subgroups.
Log
Recorded data about delivery, open, click, or bounce events.
Mail Transfer Agent (MTA)
Software that transfers email from sender to recipient.
Mandrill
A transactional email service that was formerly part of Mailchimp.
Marketing Email
Promotional email sent to lists or segments.
Message ID
A unique identifier assigned to each email.
Multi-Tenant
A system where multiple clients share the same infrastructure securely.
MX Record
DNS record that determines where to deliver incoming emails.
N–S
NDR (Non-Delivery Report)
Another name for a bounce.
Open Rate
The percentage of people who open your email.
Opt-In
The act of a user subscribing to your email list.
Opt-Out
The act of unsubscribing from a list.
Outbound Email
Emails sent from your application/system to users.
Permission-Based Email
Email sent only to people who have opted in.
Phishing
Fraudulent emails intended to trick recipients into revealing info.
Plain Text Email
Email without formatting or embedded HTML.
Postmark
A transactional email provider known for speed and reliability.
Preheader
The short text snippet that follows the subject line in inbox previews.
Queue
A backlog of emails waiting to be sent.
Rate Limiting
Controlling email sending speed to avoid throttling or blocks.
Reputation
How ISPs judge your sender trustworthiness.
Resend
A modern developer-focused transactional email provider.
Return Path
The address where bounce messages are sent.
Reverse DNS
Used by ISPs to verify that your IP matches your domain.
Role-Based Address
Emails like support@ or info@ - less personal, often blocked.
Routing
The path email takes from sender to recipient.
RBL (Realtime Blackhole List)
A list of IPs known for sending spam.
Segment
A filtered list based on behavior, demographics, etc.
Self-Hosted
Running SelfMailKit (or another service) on your own infrastructure.
Sender ID
An older authentication protocol, often replaced by SPF and DKIM.
Sender Score
A reputation score used by ESPs to measure trust.
Sending Domain
The domain you use to send emails (e.g., `yourcompany.com`).
SMTP
The protocol used to send emails from one server to another.
Soft Bounce
A temporary email delivery failure.
SPF (Sender Policy Framework)
A DNS record that lists authorized sending servers.
SPAM
Unsolicited email - usually filtered out by ISPs.
SPAM Trap
Fake email addresses used to catch spammers.
Status Code
Numeric indicators of delivery results (e.g., 250 OK).
Subject Line
The first thing a recipient sees - key to open rates.
Suppression List
List of addresses you exclude from sends (e.g., bounced or unsubscribed).
Synchronous Sending
Sending emails in real time, typically via API.
T–Z
Tagging
Applying labels to messages for filtering, analytics, or segmentation.
Template
A reusable layout for sending branded emails.
Throttling
Sending email at a controlled rate to avoid triggering spam filters.
Transactional Email
One-to-one emails triggered by user actions (e.g., receipts, password resets).
TLS (Transport Layer Security)
Encryption protocol used to protect email in transit.
Tracking Pixel
A 1×1 image used to track email opens.
Unsubscribe Link
Required for marketing emails; allows users to opt out.
UTM Parameters
URL tags used to track campaign performance in Google Analytics.
Webhooks
Server-to-server messages triggered by email events (e.g., delivery, bounce, click).
Whitelabeling
Branding SelfMailKit with your agency or product name.
Whitelist
A list of approved senders; opposite of blacklist.
Zero-Click Email
Emails that deliver value without requiring user interaction.
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