An email deliverability test checks whether your messages pass authentication, avoid blocklists and land in the inbox rather than spam. There is no single perfect test, so a reliable answer comes from combining a header check, a spam-score test, a seed-list placement test and the data mailbox providers give you.
What can a deliverability test actually measure?
Different tests answer different questions, and it helps to know which one you are running:
- Authentication test. Does the message pass SPF, DKIM and DMARC, and do the domains align?
- Spam-score test. A tool scans the content and headers and reports rule hits that look suspicious.
- Blocklist check. Is your sending IP or domain listed on a public blocklist?
- Inbox placement test. Where does the message land at Gmail, Outlook and Yahoo: primary inbox, Promotions, spam or missing?
How do you run a free deliverability test?
- Send an email from the exact system you use for campaigns, not from your personal mailbox, to a Gmail address you control.
- In Gmail, open the message, choose Show original and look at the SPF, DKIM and DMARC lines. Each should say PASS.
- Send the same message to a spam-score tester such as Mail-Tester, which gives a score out of 10 and lists what it found.
- Check the sending IP and your domain on a blocklist lookup such as the one at MXToolbox.
- Repeat with a version of your real campaign, including links and images, because a plain test message can pass when a full campaign does not.
Run the test before the first campaign from a new domain, after any change to DNS or your sending platform, and whenever open rates fall without a clear reason.
What is a seed list test?
A seed test sends your message to a set of test mailboxes at different providers and records where each copy landed. Dedicated inbox placement tools do this at scale, and our review of email deliverability tools lists the common options.
Seed results are a useful signal, not the truth. Test mailboxes have no history with your brand, while real recipients do, so engaged subscribers may see better placement than the seed shows and cold contacts worse. Look at the trend across several tests, not a single run.
How do you read the results?
Start with failures you can fix today. A failed DKIM or DMARC check, a blocklist hit or a missing unsubscribe header is concrete. A middling spam score with no obvious cause is a reason to look at content and list quality.
If authentication passes and the message still goes to spam, the cause is usually reputation, engagement or a recent change in volume. Move on to why emails go to spam and the checklist in improving email deliverability.
Which real-world data should you check next to a test?
Test tools are a snapshot. For ongoing monitoring, add Google Postmaster Tools for Gmail traffic and your sending platform's own bounce and complaint reports. The overview in what email deliverability is explains how these signals fit together.
Frequently asked questions
Is a high spam-test score proof of good deliverability?
No. It only means the message looks clean to that tool's rules. Mailbox providers also weigh your reputation and how recipients react to your mail.
How often should I test email deliverability?
Before launching from a new domain or platform, after any DNS change, and on a regular schedule such as monthly if you send often. Test immediately if opens drop suddenly.
Why does my email land in Promotions?
Gmail sorts marketing-style mail into the Promotions tab based on content and sender signals. It is still the inbox, not spam, though people see it less often.
Can I test deliverability without sending a real email?
You can check DNS records and blocklists without sending anything. Authentication results and placement need an actual message.