How to Test Emails for Spam + Best Tools

Discover how to test emails for spam to maximize email deliverability and explore the best tools available to ensure your messages reach the inbox.
Imagine you’ve spent hours crafting the perfect email campaign for your email campaign, only to find out it never reached your potential customers. Instead, it’s stuck in their spam folders.

Frustrating, right?

Well, you’re not alone. Email deliverability is a common challenge for tech startups and SaaS companies.

We’ll walk you through practical steps to check if your emails are getting marked as spam, explain how spam-testing tools work, and introduce you to the best tools available.

We've got you covered, from email preview and verification to deliverability and subject line testing. Let’s dive in and make sure your emails land where they belong – the inbox.

How Can I Check If My Emails Are Marked as Spam?

Ensuring that your emails reach the inbox, not the spam folder is crucial when sending out email campaigns.

But how can you check if your emails are being marked as spam? Let’s explore some practical steps to help you keep your emails out of the spam folder.

First, monitor your email metrics closely. Pay attention to open rates, click-through rates, and bounce rates. A sudden drop in these metrics could be a red flag that your emails end up in spam.

Next, leverage spam testing tools that analyze your email content and delivery methods, offering insights on potential spam triggers. Tools like MailGenius and GlockApps can simulate how your email will be treated by different spam filters, providing valuable feedback before you hit send.

Additionally, it’s essential to check blacklists regularly. Make sure your domain or IP address isn’t listed on major blacklists, as this can significantly impact your deliverability.

Here are some blacklists that users should check to see if their emails are being marked as spam:

  1. Spamhaus
  2. Barracuda blacklist
  3. SURBL
  4. SpamCop
  5. SORBS
  6. Invaluement
  7. PSBL (Passive Spam Block List)
  9. CBL (Composite Blocking List)
  10. Mailspike
  11. SpamAssassin
  12. SpamRats

Finally, consider asking your recipients directly. Sometimes, the best way to know if your emails are landing in spam folders is to ask your audience for feedback.

If you follow these steps—monitoring metrics, using spam testing tools, checking blacklists, and seeking recipient feedback—you can better understand and improve your email deliverability.

How Do Spam-Testing Tools Work?

how spam testing tools work
Spam-testing tools are developed to ensure your emails reach the inbox rather than getting lost in the spam folder.

Spam-testing tools function as gatekeepers, analyzing every detail of your email before it's sent out. They analyze various aspects of your email, including content, sender reputation, and technical configurations, to predict its chances of landing in the inbox.

Here’s a closer look at the process:

First, these tools perform content analysis. They scan your email for keywords and phrases commonly associated with spam, or spam-trigger words. This includes looking for excessive use of promotional language, too many links, or poor formatting. By identifying these red flags, they recommend making your content cleaner and more acceptable to spam filters.

Next, they check your reputation. Your email’s sender reputation is critical; if your domain or IP address has been flagged by spam filters, it could lower your chances of reaching the inbox. Spam-testing tools cross-reference your sender information against known blacklists to ensure you're in good standing.

Another important aspect is the spam filter simulation. These tools replicate the spam filters used by major email providers like Gmail, Yahoo, and Outlook. They simulate the delivery process and predict where your email will land—whether it will go to the inbox, promotions tab, or spam folder. This gives you a heads-up on potential issues before you even hit send.

Finally, they provide deliverability insights. After analyzing your email through various checks, spam-testing tools generate detailed reports highlighting areas for improvement. Whether tweaking your subject line, adjusting content, or fixing technical settings like SPF, DKIM, and DMARC, these insights help optimize your emails for better deliverability.

Here’s a quick rundown of what these tools do:

  • Content analysis: Scans for spammy keywords, excessive links, and suspicious formatting.
  • Reputation check: Verifies your domain and IP against known blacklists.
  • Spam filter simulation: Predicts where your email will land based on popular email providers' filters.
  • Deliverability insights: Offers detailed reports and recommendations for improvement.
Improve your email deliverability with

Best Email Spam Checker Tools

Email Preview & Spam Testing-Tools

GlockApps is a comprehensive email testing and monitoring tool that helps businesses ensure their emails are delivered to the inbox and not marked as spam.

Here are some features:

  • Inbox placement testing: Simulates email campaigns across multiple ISPs to identify deliverability issues.
  • Sender score monitoring: Tracks and provides insights on your sender reputation.
  • Blacklist monitoring: Alerts you if your IP or domain is listed on any blacklists.
  • DMARC analytics: Helps implement DMARC policies to protect your domain from spoofing and phishing.

GlockApps excels in providing detailed previews of how your emails will appear in various email clients. It also offers comprehensive spam filter testing, giving insights into how different ISPs might treat your email. This allows you to make necessary adjustments to improve deliverability before sending your campaign.
Email on Acid
Email on Acid is an email testing platform that ensures your emails look perfect in every inbox by offering robust testing and optimization tools.

Some features are:

  • Email previews: You can see how your email will render across 90+ clients and devices.
  • Spam testing: Check your email against major spam filters to identify issues before sending.
  • Accessibility checks: Ensures your emails are accessible to all users, including those with disabilities.
  • Campaign precheck: Comprehensive pre-send checklist to optimize deliverability and engagement.

Email on Acid provides extensive email previews, allowing you to ensure your email looks great on all platforms. Its spam testing feature checks your email against popular spam filters, offering suggestions to improve your email’s delivery and deliverability, and avoid the spam folder.
KickBox is a powerful email verification and email deliverability tool designed to help businesses improve their email marketing efforts by ensuring emails reach the inbox.

Some of the best features are:

  • Email Verification: Validate email addresses to reduce bounce rates and improve sender reputation.
  • Inbox Placement Testing: Analyzes email deliverability across multiple ISPs.
  • Reputation Monitoring: Monitors your IP and domain reputation to prevent deliverability issues.
  • Deliverability Consulting: Provides expert advice on improving email deliverability.

KickBox's power lies in verifying email addresses and testing inbox placement. It offers detailed analyses and reports on how your emails are perceived by spam filters, helping you make necessary adjustments to ensure maximum deliverability

Email Verification Tools

Lusha is a B2B data enrichment tool that helps sales professionals find accurate contact information, improving the efficiency of sales outreach.

Some features include:

  • Contact Enrichment: Provides up-to-date contact details, including emails and phone numbers.
  • CRM Integration: Seamlessly integrates with major CRMs to facilitate data management.
  • Prospecting Tools: Offers advanced search filters to identify high-quality leads.
  • Compliance: Ensures data privacy and compliance with email regulations like GDPR and CCPA.

While Lusha primarily focuses on providing accurate contact information, its strong integration capabilities ensure that your enriched contact data can be verified through other dedicated email verification tools.

This way, you can maintain a clean and accurate email list by cross-verifying the data provided by Lusha.
ZeroBounce is an email validation and deliverability platform designed to help businesses improve their email marketing performance by ensuring the accuracy of their email lists.

Best features:

  • Email Validation: Detects and removes invalid, inactive, and abusive emails from your list.
  • Deliverability Toolkit: Includes tools to monitor and improve email deliverability.
  • Data Append: Enriches your email list with additional information like first name, last name, and location.
  • Integration: Offers seamless integration with various email service providers and CRMs.

ZeroBounce excels at email validation, which is crucial for maintaining a healthy email list. It thoroughly checks each email address for validity, identifying potential risks such as spam traps and abuse emails. This ensures your email campaigns have a higher chance of reaching the recipient's inbox.
hunter io
Hunter is a powerful tool for finding and verifying professional email addresses, making it easier for businesses to connect with potential leads.

Here are some features:

  • Email Finder: Locates professional email addresses based on domain searches.
  • Domain Search: Identifies all email addresses associated with a particular domain.
  • Chrome Extension: Allows quick email searches directly from LinkedIn or other websites.
  • API Access: Provides programmatic access to email search and verification features.

Hunter's robust email verification feature allows users to validate email addresses in bulk or individually.

It checks for email format, domain information, and mailbox existence, ensuring the addresses in your database are valid and active. This helps maintain a high-quality email list, minimizing email bounce rates and improving deliverability.

Email Deliverability Test Tools

MX Toolbox
MX Toolbox is a comprehensive network diagnostics tool that helps businesses manage their email deliverability by offering testing and monitoring services.

Some features include:

  • Blacklist Check: Check your IP or domain against over 100 DNS-based blacklists.
  • DNS Lookup: Provides detailed information on domain name system (DNS) records.
  • SMTP Diagnostics: Analyzes SMTP settings to ensure proper email configuration.
  • Sender Score Monitoring: Tracks the reputation of your email server's IP address.

MX Toolbox excels in email deliverability tests by thoroughly diagnosing your SMTP setup and monitoring your sender score. It also offers blacklist checking, ensuring that your IP or domain is not flagged, which can severely impact deliverability.
SendForensics is an advanced email deliverability and optimization platform designed to help businesses improve their email performance through deep analysis and actionable insights.

Best features:

  • Deliverability Testing: Comprehensive testing for potential deliverability issues.
  • Content Analysis: Evaluates email content for spam triggers and compliance.
  • ISP Feedback Loop: Monitors feedback from major ISPs to track deliverability performance.
  • Comparison Reports: Benchmarks your email campaigns against industry standards for better insights.

SendForensics stands out with its in-depth deliverability testing, which includes real-time analytics and ISP feedback loops. This lets you understand how your emails perform and make necessary adjustments to optimize delivery rates.
MailGenius is a free email testing tool that helps businesses identify potential issues affecting their email deliverability and ensure their emails reach the intended recipients.

Here are the best features:

  • Spam Filter Testing: Analyzes emails against common spam filters.
  • Blacklist Monitoring: Check if your email server is listed on any blacklists.
  • Content Analysis: Scans the email content for elements that might trigger spam filters.
  • Email Authentication: Verifies SPF, DKIM, and DMARC records to ensure proper email authentication.

MailGenius provides a thorough email deliverability test by checking your emails against spam filters and ensuring your authentication records are correctly set up. It also monitors blacklist status, helping to maintain a clean sender reputation.

Subject Line Tester

omnisend subject line tester
OmniSend is an email marketing platform designed to simplify the creation and management of email campaigns. It includes special tools for optimizing subject lines.

Best features include:

  • Subject Line Tester: This person analyzes and scores subject lines based on various factors, such as length, word choice, and emotional impact.
  • Pre-Built Templates: Offers a range of professionally designed email templates.
  • Automation: Allows for sophisticated email automation workflows.
  • A/B Testing: Provides tools to test different elements of your emails, including subject lines.

OmniSend's Subject Line Tester evaluates your proposed subject lines for effectiveness. It provides insights into how your subject line might perform, helping you tweak it for better open rates by considering factors like length, sentiment, and relevance.
sendcheckit subject line tester
SendCheckIt is a specialized tool that analyzes and improves email subject lines to boost open rates and engagement.

Here are some features:

  • Subject Line Tester: Provides a detailed analysis of subject lines, highlighting strengths and weaknesses.
  • Word Bank: Suggest alternative words that can improve the effectiveness of your subject line.
  • Spam Check: Ensures your subject line won't trigger spam filters.
  • Mobile Preview: This shows how your subject line will appear on different devices.

SendCheckIt's Subject Line Tester is particularly strong in providing comprehensive feedback on your subject lines. Considering elements like word choice, length, and potential spam triggers helps you refine your subject lines to maximize open rates.
Subject Line
subject line tester
SubjectLine is a free tool dedicated to evaluating the effectiveness of email subject lines, offering quick and actionable insights.

Here are some features:

  • Subject Line Score: Gives a score of 100 based on various criteria, including length, word usage, and personalization.
  • Recommendations: It provides suggestions for improving your subject line's performance.
  • Industry Benchmarks: Compares your subject line against industry standards.
  • Historical Data: Uses data from millions of subject lines to inform its analysis.

SubjectLine's primary focus on subject line tests makes it an invaluable tool for fine-tuning email campaigns. It analyzes your subject lines against proven criteria and offers practical recommendations to improve their effectiveness, aiming for higher open rates.



Ensuring your emails reach the inbox is critical for any successful email marketing campaign.

You can significantly improve your email deliverability by regularly testing your emails for spam, verifying your email lists, and optimizing your email content. Use the best tools to maintain a high sender reputation and effectively connect with your audience.

Investing time and resources into these practices will pay off in the long run, ensuring your messages reach their intended recipients and achieve their desired impact.
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