Email, Mobile and Customer Relationship Marketing

Introduction

Email, mobile and customer relationship marketing (CRM) are central components of digital marketing because they enable organisations to communicate with known individuals over time. Unlike many paid-media activities, these channels can support continuing relationships, repeat purchases, service delivery, retention and advocacy. Their value does not arise simply from sending more messages. It depends on permission, relevance, timing, technical deliverability, customer value and responsible use of personal data.

Email marketing uses electronic messages to inform, persuade, serve and retain subscribers. Mobile marketing uses devices and mobile services—such as SMS, push notifications, mobile applications, mobile wallets and messaging platforms—to reach customers in contexts where immediacy and convenience matter. CRM coordinates customer data, interactions and relationship strategies across these and other touchpoints.

A useful relationship perspective is that each message should contribute to a customer lifecycle rather than operate as an isolated promotion. A person may first subscribe, then become a prospect, make a first purchase, receive onboarding, buy again, become inactive and eventually either return or unsubscribe. Effective marketing recognises these stages and designs communications accordingly.

Learning Objectives

By the end of this chapter, you should be able to:

• explain permission-based list building and consent management;
• distinguish segmentation, targeting and personalisation;
• design lifecycle email and mobile messages;
• describe the role of marketing automation and customer data platforms;
• calculate and interpret delivery, open, click, conversion, retention and unsubscribe measures;
• identify ethical, legal, accessibility and governance requirements; and
• recommend improvements to a channel programme using evidence.

1. Permission-Based List Building

A permission-based list contains people who have agreed to receive a defined category of communication. Permission is more than obtaining a database containing contact details. It is an expectation-setting process: the organisation should explain what will be sent, through which channel, how frequently, and how the recipient can withdraw consent.

Common acquisition methods include:

• a website subscription form;
• account registration with a separate marketing choice;
• a content download accompanied by a clear subscription option;
• checkout consent where marketing is not made a condition of purchase;
• event or point-of-sale sign-up; and
• an SMS keyword or in-application permission prompt.

A strong sign-up form uses plain language and avoids pre-ticked boxes. It should collect only information that has a genuine operational or personalisation purpose. A progressive approach may request an email address initially and ask about preferences later. Double opt-in, in which a subscriber confirms an email address through a follow-up message, can reduce invalid addresses and provide stronger evidence of consent, although it may reduce immediate list growth.

Consent is not permanent. It should be recorded with its source, timestamp, wording, channel, jurisdiction and relevant preference. Organisations should also suppress addresses that have unsubscribed, bounced repeatedly or requested erasure. Purchased lists are particularly risky because the people on them have generally not granted permission to the new sender. They can cause complaints, poor deliverability and regulatory exposure.

A valuable list is therefore not the largest list. It is a permissioned, accurate and engaged audience whose expectations match the organisation's communications.

2. Segmentation and Personalisation

Segmentation divides an audience into groups with meaningful similarities. Useful bases include:

Segmentation should be actionable. A segment is useful when the organisation can deliver a different proposition, message, timing or treatment to it. Excessive segmentation can create operational complexity and small samples that are difficult to evaluate.

Personalisation changes the content or experience for an individual or segment. It may be simple, such as using a name, or substantive, such as recommending accessories based on a recent purchase. Personalisation should be accurate and contextually appropriate. An organisation should not reveal sensitive inferences in a message merely because its systems can calculate them. For example, a health-related inference or financial difficulty should not be exposed in a promotional email without a compelling, lawful and ethical basis.

Personalisation can be described through four levels:

1. Address personalisation: name, account or location.
2. Content personalisation: products, articles or offers relevant to behaviour or preference.
3. Timing personalisation: delivery at a suitable time or after a meaningful event.
4. Journey personalisation: different sequences based on lifecycle or response.

Good personalisation improves relevance; poor personalisation produces errors, surveillance concerns or an impression of automation without understanding.

3. Lifecycle Marketing and Customer Journeys

Lifecycle marketing maps communication to the changing relationship between an organisation and a customer. A typical journey includes awareness, subscription, consideration, first purchase, onboarding, repeat purchase, retention, reactivation and advocacy. Not every customer follows this order, and the stages should be adapted to the business model.

Typical lifecycle messages include:

• Welcome: confirms the subscription, states expectations and presents a useful first action.
• Nurture: provides education, evidence, comparisons or demonstrations before purchase.
• Abandonment reminder: helps a customer return to an unfinished action, subject to privacy and channel rules.
• Transactional confirmation: confirms an order, booking, payment or service event.
• Onboarding: explains setup, usage, support and the next desired behaviour.
• Cross-sell or replenishment: recommends a genuinely related product at an appropriate time.
• Retention: recognises continuing use and provides service or value.
• Win-back: invites an inactive customer to re-engage, while offering a clear preference or unsubscribe route.

A journey should have a defined entry condition, intended outcome, message sequence, exit condition and frequency limit. For example, a welcome journey may begin after confirmed subscription, contain three educational messages, exit when a purchase occurs and stop if the subscriber unsubscribes.

The communication objective should be distinguished from the business objective. “Increase clicks” is a communication objective; “increase completed first purchases without increasing complaints” is a stronger business objective. This distinction prevents teams from optimising superficial activity at the expense of customer value.

4. Marketing Automation

Marketing automation uses rules, data and software to trigger, schedule, personalise and measure communications. A simple workflow might be:

1. A person submits a form.
2. The system validates the address and records consent.
3. A welcome message is sent.
4. A click on a product category assigns a behavioural attribute.
5. A relevant educational message is sent after a delay.
6. A purchase removes the person from prospect messages and starts onboarding.
7. Inactivity later triggers a carefully controlled reactivation journey.

Automation is not synonymous with artificial intelligence. Rule-based workflows use explicit conditions, whereas AI may assist with classification, recommendations, send-time prediction or content drafting. In both cases, marketers remain responsible for data quality, bias, message accuracy, approvals and outcomes.

A basic automation design should specify:

• event or condition that starts the journey;
• data fields required;
• decision rules and priority when conditions conflict;
• message content and channel;
• delay and frequency limits;
• exclusions, such as recent purchasers or unsubscribed contacts;
• success and failure measures; and
• human review for sensitive or high-impact communications.

Automation can create harm when outdated data, duplicate records or conflicting journeys cause irrelevant messages. Governance therefore requires an accessible journey inventory, testing, audit logs and a process for pausing communications quickly.

5. Mobile Marketing as a Relationship Channel

Mobile marketing has distinctive characteristics: immediacy, personal proximity, location awareness and frequent use. These advantages also create risk because interruptions are more intrusive than many desktop communications.

SMS is useful for urgent reminders, authentication, delivery updates and concise offers. It is constrained by character limits, cost, consent requirements and the high visibility of a personal phone. Promotional SMS should identify the sender and provide a practical opt-out mechanism where required.

Push notifications are delivered through an application and require operating-system permission. They can support timely reminders, account information and contextual features. Permission should be requested after the user understands the benefit, not immediately on first launch without explanation.

In-app messages appear while a person is using an application. They can support onboarding and feature discovery but should not obstruct essential tasks.

Mobile messaging platforms can support conversational service, notifications and commerce. Organisations must distinguish marketing messages from customer support and ensure that automation does not make it impossible to reach a human when needed.

Mobile design should use readable text, clear action controls, short copy, accessible contrast and landing pages that work on small screens. Time zones, quiet hours and local norms matter. A message that is appropriate at 10:00 in one location may be intrusive at 02:00 elsewhere.

6. Measurement and Interpretation

Metrics are indicators, not objectives in themselves. Each metric should be connected to a defined population, time period and event definition. Teams should document whether rates use delivered messages, total sends, unique recipients or total events as the denominator.

Delivery rate

Sent messages are accepted for attempted transmission; delivered messages are reported as reaching the recipient's mail or messaging system. A delivery rate may be affected by invalid addresses, blocks, temporary failures and provider definitions. It does not prove that a person saw or read a message.

Open rate

This measure assumes that the platform can record an open reliably. Tracking restrictions, privacy features, image blocking and machine-generated activity can make opens incomplete or inflated. Open rate should therefore be treated as directional, not as a definitive measure of attention.

Click-through rate

CTR indicates response to the message and its call to action. Click-to-open rate uses recorded opens as the denominator:

The latter can be useful for evaluating content among those identified as openers, but it inherits the weaknesses of open tracking.

Conversion rate

A campaign conversion rate must state its denominator. If it is based on delivered messages:

If it is based on clickers, the denominator is unique clickers instead. Attribution rules—such as last click, first click or a defined time window—can substantially change reported results. Conversion should be linked to a meaningful outcome, such as a completed purchase, application or activation, not merely a page view.

Unsubscribe rate

This measure should be interpreted alongside complaint rate, engagement, list growth and customer value. A low unsubscribe rate is not automatically good if messages are ignored or difficult to leave. Easy, visible preference and unsubscribe controls are both ethical and operationally useful.

Retention and repeat behaviour

For a cohort of customers who began in a specified period:

“Active” must be defined, such as making a purchase, using a service or opening an account within the period. Retention is not the same as repeat purchase rate unless the business defines activity as a repeat purchase.

Worked example

An organisation sends 20,000 emails. Of these, 19,000 are delivered. There are 3,800 unique recorded opens, 950 unique clickers, 190 purchases attributed under the campaign's stated attribution rule, and 76 unsubscribes.

• Delivery rate = 19,000 ÷ 20,000 × 100% = 95%.
• Open rate = 3,800 ÷ 19,000 × 100% = 20%.
• CTR = 950 ÷ 19,000 × 100% = 5%.
• Conversion rate by delivered messages = 190 ÷ 19,000 × 100% = 1%.
• Unsubscribe rate = 76 ÷ 19,000 × 100% = 0.4%.

The results suggest that delivery is reasonably strong, while the organisation should investigate the relevance of the message, the landing-page experience and the relationship between clicks and purchases. The figures do not, by themselves, prove why performance occurred.

7. Testing and Optimisation

Testing compares alternative treatments while holding other important conditions as constant as possible. Variables may include subject line, offer, call-to-action wording, creative format, send time, frequency or landing page. A test should define a primary metric before launch and avoid changing several variables simultaneously when the purpose is to learn causally.

For example, an organisation might randomly assign eligible subscribers to subject line A or B, deliver both at a comparable time, and compare conversion rather than only opens. The sample should be large enough for the decision's importance, and results should not be declared from a very early fluctuation. Where practical, a control or holdout group helps estimate incremental effect: what happened because of the communication rather than what would have happened anyway.

Optimisation should consider negative outcomes. A message that increases short-term purchases but also raises complaints, refunds or unsubscribes may reduce long-term value. A balanced dashboard can include delivery, clicks, conversions, revenue or leads, retention, complaints, unsubscribes and contribution margin.

8. Ethical, Legal and Governance Considerations

Requirements vary by jurisdiction, but responsible practice commonly includes lawful permission, transparency, purpose limitation, data minimisation, security, retention controls and rights to access or delete personal data. Marketers should consult applicable laws and organisational legal guidance rather than assume that one country's rules apply everywhere.

Key controls include:

• separate service communications from promotional consent where required;
• provide a clear and simple unsubscribe or preference mechanism;
• honour opt-outs promptly across systems and channels;
• identify the sender and avoid deceptive subject lines;
• document consent and data provenance;
• protect lists through access controls and secure processing;
• avoid sensitive targeting without an appropriate basis;
• test accessibility, including screen-reader compatibility and plain-text alternatives; and
• establish human oversight for AI-generated or high-risk content.

Fairness also matters. A model that predicts customer value may systematically exclude low-income, rural or historically underserved groups from useful offers. A frequency algorithm may over-contact highly responsive users and fatigue them. Governance should therefore review not only legal compliance but also dignity, autonomy, inclusion and the distribution of benefits and burdens.

9. Applied Case: Harbour Street Outdoor Equipment

Background. Harbour Street Outdoor Equipment is an illustrative regional retailer with an online store and three physical outlets. It has 60,000 email records, but many were imported from old sales files. Its email programme produces frequent promotions, while SMS is used irregularly for delivery notifications.

Problem. Delivery has fallen, customer complaints have increased and repeat purchases are below management expectations. The retailer cannot reliably distinguish consented subscribers from former customers who never agreed to marketing. A single weekly promotion is sent to almost everyone.

Analysis. An audit finds duplicate addresses, invalid contacts, absent consent records and no preference centre. The retailer also discovers that new customers receive no onboarding or product-care guidance. Campaign reporting focuses on opens, despite evidence that privacy controls make the measure inconsistent.

Approach. The retailer pauses promotional sends to records without defensible permission and creates a re-permission process where legally appropriate. It introduces preference choices for hiking, camping, clothing and service content, plus a frequency option. New subscribers enter a welcome journey; purchasers receive care and usage information; replenishable products receive timed reminders; inactive subscribers enter a limited reactivation sequence. SMS remains restricted to opted-in, time-sensitive messages and selected offers.

The team defines metrics before implementation: delivery rate, unique click rate, purchase conversion, unsubscribe rate, complaint rate and repeat-purchase retention. It uses a holdout group for selected journeys and reviews performance by consent source and lifecycle stage. The data team establishes suppression rules so that a purchase stops prospect messages and an unsubscribe suppresses promotional communication across channels.

Outcome. In this illustrative case, the first improvement is not a larger list but a cleaner and more trustworthy one. Delivery and complaint performance improve after invalid and unauthorised records are removed. Onboarding generates more product-use engagement, while reactivation is judged successful only when returning customers remain active rather than merely clicking a discount.

Learning points. Permission quality, lifecycle relevance, cross-channel suppression and measurement definitions are more valuable than indiscriminate volume. CRM is a coordinated relationship system, not simply a software database or a schedule of promotional broadcasts.

10. Contemporary Developments and Best Practice

Privacy changes are reducing the reliability of some tracking signals, particularly open measurement. Organisations should develop first-party relationships based on explicit value, preference data and meaningful outcomes. Preference centres, zero-party data—information intentionally supplied by the customer—and server-side measurement can improve control, but they do not remove the need for consent and transparency.

Generative AI can help draft variants, classify responses, summarise feedback or support recommendation systems. It can also reproduce bias, expose confidential data, invent claims or produce inappropriate personalisation. Approved data sources, human review, brand controls, disclosure where appropriate and performance monitoring are essential.

A practical best-practice checklist is:

1. Define the customer value and business objective before selecting a channel.
2. Collect permission in a clear, recorded and reversible way.
3. Maintain accurate, deduplicated and securely governed data.
4. Segment by relevant needs, behaviour, lifecycle and declared preference.
5. Design journeys with entry, exit, exclusion and frequency rules.
6. Make content useful, accessible, recognisable and mobile-friendly.
7. Use automation to improve service, not to remove accountability.
8. Measure outcomes with documented denominators and attribution rules.
9. Test incrementally and include negative outcomes in evaluation.
10. Make unsubscribing and changing preferences easy.

Chapter Summary

Email, mobile and CRM marketing are relationship activities built on permission, relevance and continuing value. Effective list building records meaningful consent and maintains data quality rather than pursuing maximum volume. Segmentation groups customers according to actionable similarities, while personalisation adapts content, timing or journeys without exposing inappropriate inferences.

Lifecycle marketing coordinates welcome, nurture, onboarding, retention and reactivation communications. Marketing automation operationalises these journeys through triggers, rules, exclusions and measurement, but requires governance and human accountability. Mobile channels offer immediacy and contextual value while demanding careful permission, timing, accessibility and frequency control.

Delivery, open, click, conversion, unsubscribe and retention rates are useful only when their populations, denominators, definitions and attribution rules are explicit. Open data is increasingly imperfect, so marketers should emphasise meaningful clicks, conversions, retention, complaints and incremental outcomes. Ethical and legal practice requires transparency, data minimisation, security, accessible design and prompt respect for preferences. The central principle is simple: communicate with people because the communication is expected and useful, not merely because technology makes it possible.

Key Terms

Permission-based marketing: Marketing communication sent to people who have granted appropriate permission.

Double opt-in: A confirmation process in which a subscriber verifies a sign-up request.

Preference centre: A facility through which people choose topics, channels or communication frequency.

Segmentation: Dividing an audience into groups with meaningful shared characteristics.

Personalisation: Adapting content, timing or experience to an individual or segment.

Lifecycle marketing: Communication designed for stages in the customer relationship.

Customer relationship management (CRM): The coordinated management of customer data and interactions to create mutual value.

Marketing automation: Software-supported triggering, scheduling and measurement of communications.

Trigger: An event or condition that starts or changes an automated journey.

Suppression: Excluding a person from a message because of consent, lifecycle or business rules.

Deliverability: The ability of messages to reach the intended recipient system.

Open rate: Unique recorded opens divided by delivered messages.

Click-through rate: Unique recipients who clicked divided by delivered messages.

Conversion rate: Attributed conversions divided by a specified eligible population.

Retention rate: The proportion of a defined cohort that remains active at the end of a period.

Reactivation: Communication intended to restore activity from an inactive customer.

First-party data: Data collected directly by an organisation through its own customer interactions.

Zero-party data: Information intentionally and proactively supplied by a customer.

Holdout group: A control group withheld from a communication to estimate incremental impact.

Frequency capping: Limiting how often a person receives communications within a period.

Review Questions

Short Answer Questions

1. What is the difference between a permission-based list and a purchased list?
2. Identify three useful bases for customer segmentation.
3. Why should an automated journey include entry and exit conditions?
4. What does delivery rate measure, and what does it not prove?
5. State two ethical risks associated with mobile marketing.

Long Answer Questions

1. Explain how an organisation could design a welcome, onboarding and reactivation lifecycle programme.
2. Discuss the relationship between segmentation, personalisation and customer value.
3. Explain why open rate should be interpreted cautiously and identify alternative measures.
4. Describe the governance controls required for responsible marketing automation.
5. Compare email, SMS, push notifications and in-app messages as relationship channels.

Analytical / Application Questions

1. A retailer sends 12,000 emails, of which 11,400 are delivered. There are 2,280 unique recorded opens, 456 unique clickers, 91 attributed purchases and 34 unsubscribes. Calculate the delivery rate, open rate, click-through rate, conversion rate by delivered messages and unsubscribe rate. Interpret two implications.
2. Design a permission-based lifecycle journey for a subscription service. Specify the sign-up permission, segments, triggers, messages, exclusions, success measures and unsubscribe controls.
3. An organisation's clicks and short-term sales increase after it sends daily mobile promotions, but complaints and unsubscribes also rise. Recommend an evidence-based response using segmentation, frequency control, testing and retention measures.

Multiple Choice Questions with Answers

Question 1

Which practice best demonstrates permission-based list building?

A. Buying a large list from a data broker

B. Adding all former customers to promotional email automatically

C. Explaining the communication purpose and recording an affirmative subscription

D. Sending promotional messages until a recipient complains

Correct Answer: C. Explaining the communication purpose and recording an affirmative subscription

Question 2

Which segmentation basis is most directly useful for a replenishment reminder?

A. Random assignment

B. Previous purchase timing and product type

C. Email address length

D. Alphabetical surname order

Correct Answer: B. Previous purchase timing and product type

Question 3

An email campaign sends 10,000 messages and delivers 9,500. What is its delivery rate?

A. 5%

B. 90%

C. 95%

D. 105%

Correct Answer: C. 95%

Question 4

Why should open rate be treated as a directional rather than definitive measure?

A. Every delivered email is always opened

B. Privacy controls and automated activity can affect recorded opens

C. Clicks cannot be measured

D. Unsubscribes are included in the numerator

Correct Answer: B. Privacy controls and automated activity can affect recorded opens

Question 5

Which event would most appropriately start a post-purchase onboarding journey?

A. A customer completes a purchase

B. A competitor changes its website

C. A message reaches its character limit

D. A marketer changes a colour palette

Correct Answer: A. A customer completes a purchase

Question 6

What is the main purpose of a suppression rule?

A. To increase duplicate records

B. To ensure every person receives every message

C. To exclude people who should not receive a particular communication

D. To remove all measurement from a campaign

Correct Answer: C. To exclude people who should not receive a particular communication

Question 7

A campaign has 19,000 delivered messages and 950 unique clickers. What is its click-through rate?

A. 0.5%

B. 5%

C. 19%

D. 50%

Correct Answer: B. 5%

Question 8

Which mobile practice is most responsible?

A. Sending at any hour because mobile devices are portable

B. Requesting app permission without explaining the benefit

C. Using clear permission, appropriate timing and an easy preference or opt-out route

D. Assuming a previous email opt-in always covers every mobile channel

Correct Answer: C. Using clear permission, appropriate timing and an easy preference or opt-out route

Question 9

What does a holdout group help a marketer estimate?

A. The colour of a subscriber's phone

B. Incremental impact compared with not sending the communication

C. The legal age of every customer

D. The number of invalid passwords

Correct Answer: B. Incremental impact compared with not sending the communication

Question 10

Which is the strongest business interpretation of a campaign with more purchases but sharply higher complaints and unsubscribes?

A. It is automatically successful because purchases increased

B. Negative relationship effects should be evaluated before scaling it

C. The campaign should be sent more frequently to everyone

D. The unsubscribe mechanism should be hidden

Correct Answer: B. Negative relationship effects should be evaluated before scaling it