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SMTP (Simple Mail Transfer Protocol)
The protocol email servers use to send messages across the internet. Core to email delivery.
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A/B testing
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Alt Text
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AMP for Email
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Analytics
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API
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Audience
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Automations
B
Best practices
B
Blacklist / Blocklist
B
Bounce rate
B
Bounces
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Call to action (CTA)
C
Campaign
C
Campaign editor
C
CAN-SPAM
C
CCPA (California Consumer Privacy Act)
C
Churn rate
C
Click rate
C
Click through rate (CTR)
C
Contacts
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Content
C
Conversion rate (CVR)
C
CPC (Cost Per Click)
C
CPM (Cost Per Mille)
C
Custom fields
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Deliverability
D
Delivery rate
D
DKIM
D
DMARC
D
Double opt-in
D
Drip Campaign
D
Dynamic content
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Email authentication
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Email client
E
Engagement
E
Engagement score
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ESP
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Export
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Feedback loop (FBL)
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Footer
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GDPR (General Data Protection Regulation)
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Growth
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Header
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Hero image
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Import
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Inactive subscriber
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Inbox placement
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Integrations
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IP address
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ISP
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Knowledge Base
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List fatigue
L
List hygiene
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Manage preferences
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Migration
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Monetization
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MTA (Mail Transfer Agent)
M
MX record
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Newsletter
O
Open rate
O
Opt in
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Opt out
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Partner Program
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Permission-based sending
P
Personalization
P
Plain text version
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Preference center
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Preheader text
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PTR record (Reverse DNS lookup)
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Publication
R
Re-engagement campaign
R
Rendering
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Responsive design
R
Retargeting
R
Revenue per email (RPE)
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Revenue Per Recipient (RPR)
R
RSS feed
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Safelist
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Seed list
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Segments
S
Senders
S
SMTP (Simple Mail Transfer Protocol)
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Spam trap
S
SPF
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Subject line
S
Subscribe forms
S
Subscribers
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Template
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Throttling
T
TLS (Transport Layer Security)
T
Transactional email
T
Triggered email
U
Unsubscribe
U
URL
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Webhooks
W
Welcome email
W
Whitelist