10 Best Email Testing Software for Mailing Messages in 2025

Email marketing remains one of the most effective ways to connect with customers, drive engagement, and boost revenue. But here’s the catch: if your emails don’t land in the inbox—or worse, they look broken on a recipient’s device—all that effort goes down the drain. That’s where email testing software comes in. These tools help you preview, validate, and optimize your emails before hitting "send," ensuring they perform at their best. With 2025 in full swing (as of February 26, 2025), it’s time to explore the top 10 email testing software options for mailing messages. Whether you’re a marketer, developer, or small business owner, this guide will walk you through the best tools to perfect your email campaigns.

Let’s dive in and find the right solution for your needs—no fluff, just practical insights and actionable recommendations.

Why Email Testing Software Matters in 2025

Before we get to the list, let’s talk about why email testing software is a must-have. Over 306 billion emails are sent daily, according to Statista, and that number keeps climbing. With inboxes more crowded than ever, deliverability is king. Email testing tools ensure your messages don’t end up in spam, render correctly across devices, and resonate with your audience. From checking subject lines to validating HTML, these platforms save you from costly mistakes. Plus, with new email authentication standards like Gmail and Yahoo’s 2024 DMARC requirements, testing is no longer optional—it’s essential.

SEO tip: Keywords like "email testing software," "best tools for email marketing," and "email deliverability 2025" are sprinkled throughout this article to help it rank higher on Google. Let’s get to the good stuff!

1. Mailtrap

Overview

Mailtrap is a powerhouse for developers and marketers alike. It’s an all-in-one email testing platform that lets you test, send, and monitor your email infrastructure without risking real customer inboxes. Think of it as a sandbox for your emails.

Key Features

Fake SMTP Server: Test emails in a staging environment to avoid accidental sends.

Email Previews: See how your email looks across 100+ clients and devices.

Spam Analysis: Check your spam score and tweak content to boost deliverability.

Integrations: Works with Python, Ruby, PHP, and more for QA automation.

Why It’s Great

Mailtrap shines for teams who need a safe space to experiment. Its fake SMTP server ensures you never accidentally spam your subscribers during testing. Plus, the detailed spam analysis helps you stay out of the junk folder—a critical factor in 2025 with stricter mailbox provider rules.

Pricing

Starts at $10/month for the Individual plan, with a free tier offering 100 emails/month.

Best For

Developers and small teams focused on pre-send testing and deliverability.

2. Litmus

Overview

Litmus is a veteran in the email testing world, trusted by brands like Toyota and IBM. It’s a comprehensive tool that combines preview testing, analytics, and optimization features.

Key Features

100+ Client Previews: Test across Gmail, Outlook, Apple Mail, and more—including Dark Mode.

Email Guardian: Monitors your emails 24/7 for rendering issues post-send.

Spam Testing: Checks deliverability against major spam filters.

Accessibility Checks: Ensures your emails are inclusive for all users.

Why It’s Great

Litmus cuts QA time in half with its real-time previews and automated checks. If you’re sending high-stakes campaigns, its Email Guardian feature alerts you to client-side changes (like a sudden Gmail update) that could break your emails.

Pricing

Starts at $99/month for the Basic plan, with a 7-day free trial.

Best For

Enterprise teams and marketers who need robust analytics and post-send monitoring.

3. Email on Acid

Overview

Email on Acid is a go-to for previewing and optimizing emails. It’s been a staple for marketers and developers looking to ensure flawless rendering across devices.

Key Features

90+ Client Previews: Covers popular email clients and mobile devices.

Spam Testing: Tests against 23 spam filters to improve inbox placement.

Link and Image Validation: Flags broken links or missing images before you send.

Deliverability Insights: Identifies issues like blocklisting or authentication errors.

Why It’s Great

Email on Acid’s strength lies in its simplicity and depth. The spam testing is top-notch, giving you actionable steps to avoid the dreaded spam folder. It’s perfect for anyone who wants a balance of usability and detailed insights.

Pricing

Starts at $86/month, with a 7-day free trial.

Best For

Agencies and mid-sized businesses prioritizing deliverability and design consistency.

4. Mailgun

Overview

Mailgun is primarily an email delivery service, but its built-in testing tools make it a contender for this list. It’s designed for developers who need scalable email solutions.

Key Features

Email Validation: Verifies addresses to reduce bounces.

Inbox Placement Testing: Shows where your emails land (inbox, spam, or blocked).

Template Previews: Renders emails in the control panel for quick checks.

SMTP Testing: Ensures your server setup works with providers like SendGrid.

Why It’s Great

Mailgun blends testing with delivery, making it a one-stop shop for developers. Its inbox placement testing is a standout, especially with 2025’s focus on hitting the inbox every time.

Pricing

Starts at $35/month for the Foundation plan, with a free tier for 5,000 emails.

Best For

Developers and tech-savvy marketers needing delivery and testing in one package.

5. GlockApps

Overview

GlockApps is a deliverability-focused tool that helps you understand where your emails land and why. It’s all about getting your messages to the inbox.

Key Features

Inbox Placement Tests: Checks delivery across Gmail, Outlook, Yahoo, and more.

Spam Filter Testing: Analyzes your content and sender reputation.

DMARC Analyzer: Ensures compliance with modern authentication standards.

Reputation Monitoring: Tracks your sender score over time.

Why It’s Great

GlockApps is laser-focused on deliverability, which is critical in 2025 as mailbox providers tighten their rules. The detailed reports make it easy to pinpoint and fix issues fast.

Pricing

Starts at $99/month, with a free spam test available.

Best For

Marketers and businesses obsessed with inbox placement and sender reputation.

6. Mailchimp Transactional Email (Mandrill)

Overview

Mailchimp Transactional Email, formerly Mandrill, is built for developers sending contextual emails via API or SMTP. Its testing capabilities are a bonus.

Key Features

SMTP Testing: Validates your server setup for transactional emails.

Delivery Tracking: Monitors where emails land in real-time.

A/B Testing: Tests subject lines and content for better engagement.

API Integration: Seamlessly connects with your app or workflow.

Why It’s Great

If you’re sending transactional emails (think password resets or order confirmations), Mailchimp Transactional Email ensures they’re delivered reliably. The testing features are a nice add-on for fine-tuning.

Pricing

Starts at $20/month for 500 emails, tied to Mailchimp’s ecosystem.

Best For

Developers and businesses focused on transactional email performance.

7. Moosend

Overview

Moosend is an email marketing platform with robust testing tools baked in. It’s user-friendly and affordable, making it a favorite for small businesses.

Key Features

Email Previews: Tests rendering across devices and clients.

Spam Testing: Gauges how your email fares against filters.

A/B Testing: Compares subject lines, content, and send times.

Analytics: Tracks opens, clicks, and bounces for optimization.

Why It’s Great

Moosend combines testing with campaign management, so you don’t need multiple tools. It’s budget-friendly and intuitive, perfect for beginners who still want pro-level results.

Pricing

Starts at $9/month for 500 subscribers, with a free plan for basic testing.

Best For

Small businesses and startups looking for an all-in-one solution.

8. NeverBounce

Overview

NeverBounce specializes in email verification but doubles as a testing tool by keeping your lists clean and deliverable.

Key Features

Email Verification: Removes invalid, disposable, and spam-trap emails.

Bulk List Cleaning: Processes 100K emails in ~45 minutes.

Real-Time API: Blocks bad emails at signup.

Integrations: Syncs with 90+ tools like Salesforce and SendGrid.

Why It’s Great

A clean email list is the foundation of deliverability. NeverBounce ensures your messages reach real people, reducing bounces and boosting your sender reputation.

Pricing

Pay-as-you-go starts at $0.008 per email, with a free trial for 1,000 verifications.

Best For

Anyone managing large email lists who wants to maximize deliverability.

9. ZeroBounce

Overview

ZeroBounce is another email verification heavyweight that enhances your testing efforts by ensuring your list is pristine.

Key Features

Email Validation: Detects invalid and risky emails with 99% accuracy.

Spam Trap Detection: Keeps you off blocklists.

Deliverability Toolkit: Includes inbox placement and blacklist monitoring.

API Access: Verifies emails in real-time.

Why It’s Great

ZeroBounce goes beyond verification with tools to test and improve deliverability. It’s fast, accurate, and trusted by brands like Uber and Dell.

Pricing

Starts at $18/month for 2,000 credits, with 100 free monthly verifications.

Best For

Businesses needing a reliable way to clean lists and test deliverability.

10. SendGrid

Overview

SendGrid is an email delivery platform with integrated testing tools to ensure your messages hit the mark. It’s a favorite for scalability and ease of use.

Key Features

Email Testing Tool: Previews emails and validates SMTP setups.

Deliverability Insights: Tracks inbox placement and spam risks.

Segmentation: Targets the right audience for better results.

API and SMTP: Flexible options for developers.

Why It’s Great

SendGrid’s testing tools are seamlessly integrated into its delivery platform, saving you time. It’s ideal for businesses that want to test and send from one dashboard.

Pricing

Starts at $19.95/month for 40,000 emails, with a free plan for 100 emails/day.

Best For

Growing businesses and developers needing a scalable, test-friendly solution.

How to Choose the Best Email Testing Software for You

With so many options, how do you pick the right one? Here’s a quick guide:

For Developers: Go with Mailtrap, Mailgun, or Mailchimp Transactional Email for API flexibility and SMTP testing.

For Marketers: Litmus, Email on Acid, or GlockApps offer deep insights into rendering and deliverability.

For Small Businesses: Moosend and SendGrid provide affordable, all-in-one solutions.

For List Hygiene: NeverBounce or ZeroBounce are your best bets.

Consider your budget, team size, and whether you need testing as part of a broader email platform. Many tools offer free trials, so test a few before committing.

Tips to Maximize Your Email Testing in 2025

Test Across Devices: Over 50% of emails are opened on mobile, per Litmus stats. Always preview on phones and tablets.

Check Authentication: Use DMARC, SPF, and DKIM to comply with 2025 standards.

Monitor Spam Scores: Aim for a score below 5 on tools like SpamAssassin.

A/B Test Everything: Subject lines, CTAs, and send times can make or break engagement.

Clean Your List Regularly: Verification tools like NeverBounce keep your sender score high.

The Future of Email Testing in 2025

As we move deeper into 2025, email testing will evolve with AI and stricter regulations. AI-powered tools will predict deliverability issues before they happen, while mailbox providers will demand flawless authentication. Staying ahead means adopting software that adapts to these trends—like the ones on this list.

Final Thoughts

Email testing software isn’t just a nice-to-have—it’s your ticket to inbox success in 2025. Whether you’re fine-tuning designs with Litmus, sandboxing with Mailtrap, or cleaning lists with ZeroBounce, these tools ensure your messages shine. My top pick? Mailtrap for its versatility and developer-friendly features, but your choice depends on your goals.

Ready to up your email game? Try one of these tools today and watch your campaigns soar. Have a favorite I missed? Drop it in the comments—I’d love to hear your thoughts!