5 Powerful Preview Tools For Validating Your Custom Email Templates

How your emails render across email clients and devices is not just an aesthetics issue. It has to do more with user experience and engagement. And deliverability? Yes, that, too. The relationship is simple, but not the outcome.

This is why some of your emails look like they went through hell before reaching your subscriber’s inbox. These broken email campaigns are caused by what email nerds call email client rendering inconsistencies.

The custom email templates that look flawless in your email builder become a hot mess in some subscribers’ inboxes. Sometimes, images get blocked, alt text vanishes, your custom fonts suddenly default to Times New Roman (okay, not that bad), and colors invert like they have an identity crisis.

While such things happen all the time, catch them early on, before hitting the send button. If you don’t, it will break the trust you have built with subscribers and damage your reputation. Hence, you must ensure that the layout and images you decided for your emails come out as they are or are mangled on different platforms.

That’s why email preview tools have become a prominent staple for all email marketers. Like spellcheck is to writers.

To help you decide which email preview tool is right for your team, we have compiled a list of 5 of the best email preview tools on the market today.

The Importance of Previewing Your Custom Email Templates

Custom email templates are the tuxedoes of email templates. Designed to fit your brand’s needs. Its custom development, if done well, offers you code that is clean and optimized. The benefit is pixel-perfect email designs that are optimal for compatibility across major email clients and devices.

Still, if the custom-coded emails are too complex, rendering issues will occur. Complex code, unsupported elements, or overlooked fallbacks cause your custom design to break into some inboxes. Nonetheless, with services like Email Mavlers, rigorous testing across major platforms becomes the norm.

That’s why email previewing.

Email previewing is the final check that tests if your email template designs look consistent across different inbox environments. It gives screenshots of test emails showing your HTML email’s appearance when opened in different email clients and devices.

Why does email previewing matter so much?

• Incorrect rendering of HTML code degrades your professional-looking emails into amateurish.
• Your brand credibility gets judged in seconds when an email renders (or fails to).
• Poor rendering impacts your metrics— opens, clicks, and conversions.
• Dark mode compatibility has moved from nice-to-have to must-have.
• Correctly rendered emails have lesser chances of being flagged as spam.
• Knowing when you need fallbacks saves you the horror of rendering failures.
• It guarantees email responsiveness.

5 Of The Best Email Previewing Tools

1. Litmus

Email marketers who don’t use Litmus are often the same ones wondering why their open rates are suffering.

Litmus is a powerhouse tool for email testing and development designed to streamline the creation, testing, and optimization of email campaigns. It offers comprehensive previews across email clients and devices, including desktop, mobile, and web-based platforms.

Key Features

• Comprehensive Email Previews – Litmus offers real-time previews in 100+ popular email clients, including Gmail, Outlook, Apple Mail, and Dark Mode views.
• Spam Testing –
  It checks your authentication protocols and flags potential deliverability roadblocks.
• Automated QA Checks – Automated validation for critical elements like links, images, subject lines, and preview text. It also provides actionable insights to fix errors quickly.
• Chrome Extension – Users can test emails directly within their ESP using the Litmus Chrome extension.

Pricing

• Free trial: 7-day free trial available.
• Litmus Basic: $99/month (1,000 email previews)
• Litmus Plus: $199/month (2,000 email previews)
• Litmus Enterprise: Custom pricing for bigger teams with bigger needs

2. Email On Acid

The name says it all. Email on Acid is an all-in-one email testing and preview tool popular for its advanced email testing features. These features, combined with an intuitive interface, enable flawless email rendering across 100+ email clients and devices.

Its dual-testing capability—Email Testing and Campaign Precheck- stands out to us. Through a complete set of features, marketers and developers can detect and fix issues. Such as poor formatting, and code and link errors. The platform also supports team collaboration. Users can comment, edit, and review directly within the tool.

Key Features

• Email Testing Across 100+ Clients – Email on Acid provides live previews of emails across a wide selection of clients and devices.
• Campaign Precheck – It runs a predefined checklist to validate every aspect of an email. Think accessibility, URLs, UTM parameters, and spell-checking hidden HTML elements like alt text and preheaders.
• Built-in Dark Mode Optimization – Tests and optimizes email templates in darker backgrounds.

Pricing

• Free trial: 7-day free trial available.
• The Basics: $74/month with unlimited previews
• Premium: $134/month with unlimited previews plus advanced features
• Enterprise: Custom pricing based on requirements

3. Mailtrap

Mailtrap functions as a multifunctional email previewing and testing tool. It helps developers test emails before deployment into development and staging platforms. Through the virtual SMTP server functionality Mailtrap receives your outgoing emails within a secured testing space that protects your real users from receiving erroneous emails.

The tool provides teams with a protected environment suitable for newsletter and transactional email testing.

Key Features

• Sandbox Environment – It prevents mistakes like sending incomplete or incorrect emails to customers.
• Comprehensive Email Inspection – Thoroughly inspect the HTML and plain text versions of emails. The tool also highlights broken links, missing images, and formatting issues.
• API Integration – The Mailtrap API enables the automation of email testing processes, making it easier for teams to integrate testing into their workflows.
• Team Collaboration – Multiple team members can access the same inbox, making review processes smoother.

Pricing

• Free Plan: Basic functionality (500 test emails per month)
• Individual Plan: $14.99/month (5,000 test emails)
• Team Plan: $34.99/month (15,000 test emails)
• Business Plan: $64.99/month (50,000 test emails)
• Premium Plan: $129.99/month (100,000 test emails)
• Enterprise Plan: $399.99/month (up to 10 million test emails)

4. Email Preview Services

The former PreviewMyEmail platform now operates as Email Preview Services. It generates real illustrations of emails across 50 common email applications. Users can find spam testing together with analytics and an easy-to-use drag-and-drop editor as features on the platform. Email Preview Services offers an affordable and straightforward service that addresses both email performance and quality issues.

Key Features

• Spam and Blacklist Checks – It compares your IP address against over 50 blacklists, including Spamhaus and SORBS. Detecting and resolving spam-related issues to improve deliverability.
• Flexible Testing Options – Upload HTML, paste code directly, or send to a dedicated inbox—whatever fits your workflow.
• Drag-and-Drop Email Editor – The built-in editor allows users to create or modify templates easily without requiring advanced coding skills.

Pricing

• Free trial: 7-day free trial available
• Standard Plan – $25/month for unlimited email previews
• Business Plan– $45/month for unlimited email previews
• Professional Plan – $160/month for unlimited email previews
• Enterprise Plan – $399/month for unlimited email previews

5. SendForensics

SendForensics operates as an all-in-one solution combining functionality for email deliverability assessment and preview check. The platform is user-friendly. After signing up, users send an email to a dedicated address, and within seconds, a detailed analysis is available on the SendForensics dashboard.

This email preview tool stands out because it integrates deliverability scoring with infrastructure checks and content optimization and real-device email previews. The tool helps teams create visually consistent email templates without spam triggers or compliance issues that jeopardize deliverability.

Key Features

• Deliverability Snapshot – A single-glance snapshot with key metrics. Deliverability score, infrastructure analysis, and content health.
• Content Analysis – Identify and fix problematic content elements. The platform highlights spam triggers, validates links, flags HTML code issues, and detects improper data collection practices.
• Compliance Checks – You can get your templates reviewed for legal compliance by checking for unsubscribe links and cookie forensics.
• Infrastructure Validation – The tool verifies the setup and authentication protocols of your sending domain.

Pricing

• No free trial
• Starter Plan – $49/month for unlimited client previews
• Business Plan – $79/month for unlimited client previews
• Agency Plan – $199/month for unlimited client previews
• Enterprise Plan – Starts at $349/month for unlimited client previews

Wrapping Up

The truth about email marketing is—perfect-looking custom email templates can arrive as disasters in your subscribers’ inboxes. There is zero chance you can consistently create flawless emails without testing. None. Even the most experienced email pros know this.

So, always use an email previewing tool before sending. It’s not an extra step. It protects everything else you’ve worked for.

About the Author

Balaji Thiyagarajan – with over 15 years navigating diverse marketing disciplines, he brings a wealth of experience to email marketing. His expertise blends branding, demand generation, and consumer behavior insights to create impactful strategies. Currently building and scaling services at Mavlers, Balaji is passionate about sharing his marketing perspectives, particularly in areas like email marketing, lifecycle marketing, and leveraging marketing automation platforms.