The working vocabulary of email, lifecycle, and CRM marketing used across this bundle, from customer data and segmentation through channels, design, and measurement.
Sender Policy Framework. DNS record authorising which servers may send for your domain.
DKIM
DomainKeys Identified Mail. A cryptographic signature verifying the message was not altered and came from an authorised source.
DMARC
Policy telling receivers what to do on SPF or DKIM alignment failure, with aggregate reporting.
BIMI
Brand Indicators for Message Identification. Puts a verified logo into supporting clients, on top of aligned DMARC.
MPP
Apple Mail Privacy Protection. Prefetches images through Apple proxies, inflating and corrupting the open metric.
Deliverability
Whether mail reaches the inbox rather than spam. One layer below the category aware retrieval gate.
Category-aware retrieval gate
The quality-and-engagement layer above classical spam filtering that decides whether mail is surfaced in intelligent inbox views, search, and assistant answers. A sender can pass authentication and still fail it.
One-click unsubscribe
A List-Unsubscribe-Post header (RFC 8058) that lets a recipient opt out in a single tap from the inbox UI. Required of bulk senders alongside the in-body link.
Bounce
A failed delivery. Hard bounces are permanent and must be suppressed immediately; soft bounces are transient.
Sender reputation
The provider’s running assessment of a sending domain and IP, driven heavily by engagement.
List and data
Term
Meaning
Single opt in
Subscriber added on form submission, no confirmation step.
Double opt in
Subscriber must confirm via a link before being added. Better for quality and consent records.
Soft opt in
A narrow lawful basis (PECR) for marketing existing customers about similar products without prior express consent, provided an opt-out was offered at collection and in every message.
Sunset
Moving persistently disengaged contacts out of regular sending, after a re-engagement attempt fails, to protect deliverability for the active cohort.
List decay
The continuous loss of a list’s value as contacts change addresses, disengage, or go dormant; net list growth is acquisition minus decay.
Database health
The ongoing practice of keeping the contactable list deliverable and valuable through hygiene, re-engagement, and sunsetting.
Lead magnet
An incentive offered in exchange for contact details.
Segment
A subset of the list, dynamic (auto updating) or static (fixed at creation).
Merge tag
A placeholder replaced with subscriber specific data at send time.
Suppression list
Addresses that must never receive mail: unsubscribes, complaints, hard bounces.
Zero party data
Data a customer proactively and voluntarily shares. The cleanest signal.
First party data
Data from direct interactions with your own platforms.
Third party data
Data bought from outside aggregators. Fading as third-party cookies are phased out.
Customer data and CRM
Term
Meaning
CRM
Customer relationship management. The system of record for known customers and the interactions with them.
CDP
Customer data platform. Ingests data from every source, resolves identity, and maintains an activation-ready unified profile.
Data warehouse
Central store built for analysis and reporting at scale, not real-time activation.
Single customer view
One unified profile per person, assembled from every source.
Identity resolution
Stitching identifiers across devices and channels into one customer profile.
Segmentation and lifecycle
Term
Meaning
RFM
Recency, Frequency, Monetary. A behavioural segmentation model scoring customers on how recently, how often, and how much they buy.
CLV / LTV
Customer lifetime value. The total past and predicted value of a customer over the relationship.
Propensity model
A model predicting the probability a customer takes an action, such as buying or churning.
Churn
A customer lapsing or ending the relationship; churn rate is the share who do so in a period.
Retention rate
The share of customers retained over a period; its inverse is churn.
Lifecycle stage
Where a customer sits in the journey: acquisition, onboarding, engagement, retention, or winback.
Winback
The lifecycle stage, and the messaging it carries, that tries to reactivate a lapsed customer before suppressing the unresponsive.
Engagement score
A composite measure of how recently and often a contact engages (opens, clicks, sessions, purchases), used to trigger lifecycle stage transitions.
Engagement tier
An engagement score banded into a few groups, such as active, moderate, and dormant, used to set frequency caps and channel eligibility.
Loyalty program
A structured points, tier, or referral scheme that rewards repeat business.
Referral
Acquisition through an existing customer recommending the brand.
Channels and design
Term
Meaning
Transactional message
A message sent in response to a customer action or relationship (receipt, password reset, shipping update), governed by the contract rather than marketing consent. Distinct from a marketing message by primary purpose.
Marketing message
A message sent to drive a commercial outcome (campaign, promotion, winback), requiring marketing consent and an unsubscribe path.
Triggered (behavioural) message
A send fired by a customer’s behaviour or state, rather than a schedule.
Broadcast (batch)
A send to a segment on a schedule.
Orchestration
Deciding, per customer and moment, which message goes on which channel, and whether to send.
Frequency cap
A hard ceiling on messages per channel and in total over a rolling window.
Preheader (preview text)
The snippet shown after the subject line in the inbox; the third part of the envelope.
Responsive design
Layout that adapts to the screen it renders on; most email opens are on mobile.
Dark mode
A client display mode that recolours messages; designs must survive the inversion.
Alt text
Text shown in place of an image that is blocked or fails to load.
A2P 10DLC
The US registration standard for application-to-person SMS over long codes.
RCS
Rich Communication Services. The richer successor to SMS, with branding, cards, and read receipts.
APNs / FCM
Apple Push Notification service and Firebase Cloud Messaging, the two push delivery pipes.
Metrics
Term
Meaning
Open rate
Share of delivered mail where the pixel fired. Corrupted by MPP; directional only.
Click through rate
Share of delivered mail that produced a link click. The workhorse metric.
Click to open rate (CTOR)
Clicks divided by opens. Content engagement, independent of open noise.
Conversion rate
Share that produced the downstream target action. The metric that pays.
Complaint rate
Share marked as spam. A hard deliverability limit; keep under 0.1%.
Reply rate
Share that replied. A strong positive inbox signal even at 1 to 2%.
Decisioning and measurement
Term
Meaning
Decision support
Machine learning that assists a journey the marketer designed.
Decisioning
Machine learning that decides per user what to send, when, and whether to send at all.
Holdout
A randomised group deliberately left unmessaged, to measure incremental effect.
Uplift
The incremental effect of sending, against an identical user left alone.
Persuadable
A user a message wins over who would not have acted otherwise.
Contextual bandit
An algorithm that balances exploring uncertain options against exploiting known good ones.
CUPED
Controlled experiment using pre experiment data. A variance reduction technique.
DiD
Difference in differences. Estimates an effect by comparing change across treated and untreated cohorts over a date.