Check Email Deliverability

An email deliverability check is a diagnostic test to see where your emails land. Instead of sending a campaign and hoping for the best, you send a test email to a 'seed list' of inboxes controlled by a testing service (like GlockApps or Mail-tester.com). The service then reports back on inbox placement, spam scores, and potential blocklist issues.

This isn't about checking if an email address is valid; it's about verifying that your sending infrastructure—your domain, inbox, and IP—has a good enough reputation to bypass spam filters at major providers like Google and Microsoft.

An email deliverability check is a diagnostic test to see where your emails land. Instead of sending a campaign and hoping for the best, you send a test email to a 'seed list' of inboxes controlled by a testing service (like GlockApps or Mail-tester.com). The service then reports back on inbox placement, spam scores, and potential blocklist issues.

This isn't about checking if an email address is valid; it's about verifying that your sending infrastructure—your domain, inbox, and IP—has a good enough reputation to bypass spam filters at major providers like Google and Microsoft.

Guessing about your deliverability is a fast way to burn through domains and kill your pipeline. Regular checks are non-negotiable for serious teams.

1. Diagnose problems before they scale. A failing test on a single inbox is a warning sign. A failing campaign across thousands of prospects is a disaster that can destroy a domain's reputation. Checks help you catch issues when they're small and fixable.
2. Protect your sending infrastructure. High bounce rates, spam complaints, and sending to spam traps damage your domain reputation. Regular checks help you catch technical misconfigurations (like broken DNS records) or blocklist entries before they cause permanent harm.
3. Isolate campaign variables. If reply rates are low, is it the copy, the offer, or your deliverability? A deliverability test helps you rule out technical infrastructure issues, allowing you to focus on optimizing campaign content with confidence.

A proper test is more than just sending an email to your personal Gmail account. Follow a structured process to get accurate data.

1. Verify Technical Foundations First. Before sending any test, use a free tool like MXToolbox to confirm your SPF, DKIM, and DMARC records are set up correctly. A simple DNS error is a common and easily fixable cause of poor deliverability.
2. Use a Dedicated Testing Tool. Services like GlockApps, Mail-tester.com, or NeverSpam maintain seed lists across dozens of providers (Google Workspace, Outlook 365, Zoho, etc.). This gives you a comprehensive report that a single test to your own inbox can't provide.
3. Test Your Exact Campaign Email. Don't send a simple "Hello, test" message. Use the exact subject line, body copy, signature, and tracking links from your actual campaign. Spam filters analyze the entire payload, and your real content might trigger filters that a simple test won't.
4. Send from a Warmed-Up Inbox. Always run tests from the actual, fully warmed-up inboxes you use for your campaigns. Testing from a brand-new, cold inbox will always yield poor results and won't give you an accurate reading of your domain's true reputation.

1. Testing only once. Your reputation isn't static. A domain that's healthy today could be on a blocklist tomorrow after a problematic campaign. Make deliverability testing a standard part of your pre-launch checklist.
2. Ignoring the details. Don't just look at the overall score. Dig into the report. Are you landing in spam only on Microsoft inboxes? That points to a specific issue with Outlook's filters. Is your SpamAssassin score high? That indicates a problem with your copy or formatting.
3. Blaming the tool. Deliverability testers simply report what mailbox providers are doing with your email. If your emails land in spam, the problem lies with your domain, inbox, authentication, or content—not the testing service. Use the data to find and fix the root cause.

Teams sending cold outbound at scale need to understand and regularly check deliverability to keep their domains, inboxes, and reply rates healthy. It's a core discipline of managing your sending infrastructure.