What is email testing? 

Email testing is a broad term encompassing all the tests you can conduct on an email before sending it to the intended recipients. It is a quality assurance process that verifies deliverability to inboxes and guarantees the functionality of all interactive components within the email.

Why is email testing essential?

Imagine a user signing up for your service, eagerly awaiting a verification email. But it never arrives. Frustration sets in, and they abandon the process. All the resources and effort invested in driving traffic to your landing page? They vanish in an instant, rendering it all futile. This scenario highlights the critical role of email testing. Here's why it's a non-negotiable for developers and businesses:

• Prevents user abandonment: Dysfunctional email workflows lead to lost users.
• Improves engagement: For example, SaleCycle reports that cart abandonment emails have an open rate of around 40%, which is particularly impressive when you compare it to the average email open rate of 21.33%.
• Improves deliverability: Testing helps identify email content and sender reputation issues that might trigger spam filters.

Types of email testing

Understanding what you want to test is essential to choosing an appropriate tool. Based on the context and objectives, we can classify email testing into different types:

In the context of the scope and focus of testing:

End-to-end testing (E2E testing) is a software testing method that evaluates the entire application flow from start to finish. It simulates real user interactions with the application, uncovering potential inconsistencies that might hinder a smooth user flow.  

End-to-end email testing tests the entire email journey when testing an application. It's ideal for critical email flows like user signups, transactional emails, and drip campaigns. You would typically use disposable email addresses to help you simulate the email journey from the user's point of view. A service like testmail.app can help you automate this process by providing disposable email addresses that you can retrieve via an API. End-to-end email testing usually integrates with development workflows and is mainly used by developers and Quality Assurance (QA) teams.  

Component-based testing checks aspects of functionality and deliverability, emphasizing the email's design and content. This can include features like image rendering across different email clients, A/B tests, formatting, and accessibility. Email marketers typically use this type of testing for promotional campaigns.

In the context of the software development lifecycle:

Sandbox tests are the most isolated tests, often conducted in a specially created environment separate from other development activities. This isolation is crucial to avoid embarrassing mistakes like sending test emails to actual customers.

Pre-production tests occur after core development is complete and involve simulating a production environment as closely as possible. It aims to identify and fix bugs or issues before deploying the software to actual users.

Production tests are the final tests conducted after the software has been deployed to the live environment (production). They verify functionality in a real-world scenario and often involve monitoring for issues and user feedback. For example, they confirm that the email servers are working as expected or track engagement metrics to assess the effectiveness of your email campaign.

Based on the level of automation

Automated testing involves utilizing testing frameworks and tools that can automate repetitive tasks like delivery verification and basic functionality checks, freeing up time for more complex scenarios.

Manual testing involves manually sending test emails, reviewing content across different platforms, and verifying functionality through user interaction.

Based on the aspects you want to evaluate

Functional testing verifies that each feature of a software application operates correctly and meets its intended purpose as per the specified requirements. For example, functional testing might ascertain that the unsubscribe links function as expected.

Non-functional testing in email testing evaluates attributes such as performance, reliability, scalability, security, and usability, ensuring overall email system quality by assessing how well it performs under different conditions. For instance, you can conduct load testing to evaluate how the email system handles a large volume of emails sent simultaneously.

Email components you can test 

Below are examples of standard email components that undergo testing, along with the criteria against which they are evaluated:

Textual components: Clarity, relevance, length, formatting, spam triggers and personalization

• Subject line
• Body text
• Headers and salutations

Visual components: Load time, resolution, rendering, accessibility, placement, consistency with brand guidelines and visual appeal

• Images
• Graphics and icons
• Colors and branding elements

Interactive components: Usability, design, functionality, and placement

• Links
• Buttons
• Forms and surveys
• Attachments

Dynamic components: Accuracy, relevance, dynamic data population, rendering consistency, functionality

• Personalization tokens
• Conditional content
• Countdown timers

Accessibility components (e.g., WCAG)

• Alt Text for images:
• Text-to-speech compatibility
• Color contrast

Use cases

Here are a few scenarios where email testing would be helpful:

User registration and account verification: Testing the email verification process ensures that users can successfully register for an account on a website or application and verify their email addresses to activate their accounts.

Password reset functionality: Verifying the process ensures that users can securely reset their passwords via email when they forget their login credentials.

Transactional emails: Testing transactional emails such as order confirmations, shipping notifications, and invoice receipts ensures that customers receive timely and accurate information about their transactions.

Drip email campaigns: Testing drip email campaigns, such as welcome emails, onboarding sequences, and promotional newsletters, ensures subscribers receive relevant and engaging content at the right time.

Notification emails: Testing notification emails for events such as new messages, friend requests, or activity updates ensures that users receive timely alerts and stay informed about essential actions within the application.

Subscription management: Testing subscription management emails, such as subscription confirmations, renewal reminders, and cancellation confirmations, ensures subscribers have control over their subscription preferences.

Event registration and reminders: Testing event registration emails and reminders ensures that attendees receive event details, confirmations, and reminders leading up to the event.

Define your scope

Identify email system components for testing and set clear goals. For instance, your objective could be to optimize deliverability or to conduct end-to-end email flow tests for the above use cases.

Choose your tools

Explore and select tools based on specific needs. Some focus on features like spam testing, while others offer comprehensive solutions.

You can try free temporary email address generators if your testing requirements are minimal. These services provide disposable email addresses for short-term use. However, they may not be optimal for intricate test cases or test data storage requirements. 

If you are a software developer or a Quality Assurance tester, you will need many more email addresses and additional features to simplify and automate your tests. In such cases, it is best to use an end-to-end email testing service like testmail.app, where you can create unlimited email addresses, retrieve them via an API, and test for more complex cases using advanced features.

Craft test cases

Determine what actions will initiate the email flow, such as signing up for a newsletter or making a purchase. Outline the steps that follow each trigger, like sending a welcome email or a confirmation message. Identify scenarios that might fall outside the norm, like invalid email addresses or users not receiving emails. Anticipate potential issues and test how your system handles them.

Let's say you want to test the email flow for new user-signups; example test cases would be:

Positive tests: The focus of positive test cases is to verify that the system functions as intended under normal operating conditions:

• Valid signup: Verify that the user receives a confirmation email with a welcome message and login instructions.
• OTP validity: Test that the OTP has a reasonable validity period.

Negative tests: They primarily focus on ensuring the system handles invalid inputs and unexpected user behavior gracefully:

• Duplicate email submission: Test what happens when a user attempts to sign up with an email already associated with an account
• Full inbox: Test signup where the user's email inbox is full.

Edge cases: They explore the boundaries of the system's functionality and identify potential vulnerabilities under unusual circumstances:

• Email Service Provider (ESP) issues: Simulate service disruptions or delivery errors.
• Payment gateway integration: Simulate potential errors like declined credit cards or network timeouts.

Manual testing is time-consuming and repetitive, prompting the use of automated testing frameworks. These frameworks streamline testing by allowing reusable scripts across various email flow scenarios, reducing manual effort and oversight. They also offer features like scheduling, reporting, and CI/CD integration, facilitating collaboration among team members.

Popular end-to-end testing frameworks

• Selenium WebDriver: Open-source and works across various browsers, making it a versatile choice.
• Cypress: Ideal for front-end UI testing with a focus on ease of use and fast feedback loops.
• Playwright: Powerful tool for testing web and mobile apps, offering record and playback functionalities for test creation.
• Appium: Specifically designed for mobile app testing across different platforms (iOS, Android).
• Katalon Studio: A user-friendly framework that supports various testing types (web, API, mobile).

Capture and communicate

Following test execution, create a report documenting the tests run, their results (pass/fail), and any relevant details like error messages or screenshots. By integrating these reports with project management tools or dashboards, stakeholders gain insights from the testing process and identify any issues that require attention.

Now that we have seen an overview of the testing process, here are additional factors to consider when testing emails.

Optimizing email deliverability

While you want to ensure your emails reach the customer (email delivery rate), you also want to check whether they are landing in the inbox or vanishing into the abyss of the spam folder. (Email deliverability rate)

Here are a few factors you can optimize to increase your email deliverability:

Sender reputation: Sender reputation management is a critical aspect of email deliverability that directly impacts whether your emails reach recipients' inboxes or get filtered as spam. It's a score assigned to you by email providers (like Gmail and Yahoo) that reflects your trustworthiness as a sender. Several factors contribute to your sender reputation score, including bounce rate (emails that fail to deliver), spam complaints, engagement metrics (opens, clicks), and authentication protocols.

testmail.app can help you build a good sender reputation by providing a safe and controlled testing environment with disposable email addresses before your emails are sent to actual subscribers. You can spam-test your content and verify email authentication protocols like SPF, DKIM, and DMARC. 

Email infrastructure: Your email infrastructure plays a key role in deliverability, including components like mail servers, email agents, and IP addresses. Using a dedicated IP address helps isolate your sending reputation, while authentication protocols like SPF, DKIM, and DMARC ensure your emails are verified and less likely to be marked as spam. Maintaining a clean server reputation by avoiding spam traps, minimizing bounce rates, and following best practices is crucial.

Sending practices: Sending practices also affect deliverability. Managing email volume and frequency prevents triggering spam filters, and gradually increasing volume (IP warm-up) builds trust with ISPs. Segmentation and targeting are equally important; sending personalized, relevant content to segmented user groups boosts engagement rates, which ISPs monitor as an indicator of email quality.

Ensuring email security

Securing email accounts and communications is vital to thwarting a range of threats, including phishing attacks, malware distribution, and unauthorized access to confidential information. Make your emails safer through:

• Multi-factor authentication (MFA) adds an extra security layer by requiring more than just a password (e.g., a code sent to your phone).
• Email encryption: Scrambles email content, ensuring only authorized recipients can access it.
• Spam filters & anti-malware: Blocks malicious emails containing phishing attempts, malware, or harmful links.
• User training: Empowers users to identify and avoid email security threats.
• Email authentication protocols (SPF, DKIM, DMARC): Verifies the legitimacy of incoming emails and prevents impersonation attacks.

Head to Are your emails secure? for a full breakdown.

Meeting regulatory requirements

Email regulatory compliance is essential to protecting individuals' privacy, securing sensitive information, and maintaining trust in electronic communications. Failure to comply with email regulations can result in significant penalties and fines for organizations.

Key principles to ensure compliance:

• Collect and process only necessary data.
• Ensure data accuracy, limit storage, and maintain confidentiality with robust security measures.
• Do not send commercial messages without consent, including emails, social media, and text messages. Obtain freely given, specific, and informed consent using clear and straightforward language.
• Use subject lines that honestly reflect the content of the email.
• Provide clear, easy-to-follow instructions for recipients to opt out of future marketing emails, including a visible unsubscribe link.

Major regulations that apply to email communications:

• GDPR (General Data Protection Regulation)
• CAN-SPAM Act (Controlling the Assault of Non-Solicited Pornography And Marketing Act)
• CCPA (California Consumer Privacy Act )
• CASL (Canada's Anti-Spam Legislation)

Check out Email regulatory compliance simplified for a detailed guide.