Your open rate dropped and you don't know why. Are your emails landing in spam? In the Promotions tab? Or not arriving at all?
An email deliverability test answers that question. The direct answer first: the fastest way to test email deliverability is to send a real campaign email to a handful of your own seed inboxes (Gmail, Outlook, Yahoo) and see where it lands, then run the same message through a free scoring tool like mail-tester to find out why.
That two-step combo catches most problems. Below are seven ways to check where your emails land — from thirty-second checks to ongoing monitoring — and what to do with what you find.
What Is an Email Deliverability Test?
An email deliverability test is any check that tells you whether your emails reach the recipient's inbox — as opposed to the spam folder, a secondary tab, or nowhere at all.
That last distinction matters. Delivery means the receiving server accepted your message. Deliverability means it actually reached the inbox where humans look. Your sending tool can report "delivered" while every message quietly rots in spam. That's exactly why you test: your own dashboard can't see inside the recipient's mailbox.
No single test shows the whole picture. Inbox placement depends on your authentication records, domain reputation, content, list quality, and each provider's filtering. So treat the seven methods below as a toolkit, not a menu — the more of them you run, the clearer the diagnosis.
How Do You Test Email Deliverability? 7 Methods
1. Run a seed-list test
The simplest test and still the most honest one.
Create free mailboxes at the providers your audience actually uses — at minimum Gmail, Outlook, and Yahoo. Add a Google Workspace and Microsoft 365 address if you sell B2B, because business filtering differs from consumer filtering. That's your seed list.
Now send your real campaign email — same sending tool, same domain, same content — to those seeds. Then open each mailbox and record where the message landed: inbox, spam, or Promotions.
Do this before every major campaign and once a week during normal sending. It takes five minutes and catches placement problems your analytics never show.
One caveat: seed inboxes have no engagement history with you, so results skew slightly pessimistic. If a message hits the seed inbox, that's a great sign. If it hits spam everywhere, you have a real problem.
2. Score your setup with mail-tester
Go to mail-tester.com and it shows you a unique throwaway address. Send your campaign email to that address from your sending tool. Click "check your score."
You get a score out of 10, with an itemized breakdown: whether SPF, DKIM, and DMARC pass, whether your sending IP appears on blocklists, how spam filters judge your content, and whether technical details like your reverse DNS look right.
The gold is in the breakdown, not the number. A missing DKIM signature or a broken list-unsubscribe header is a concrete, fixable finding. Aim for 9 or higher, fix what it flags, and retest.
3. Monitor Google Postmaster Tools
If Gmail matters to your audience — and it almost always does — this is non-negotiable.
Google Postmaster Tools is Google's free dashboard for senders. Add your domain, verify it with a DNS record, and once you're sending enough volume, Google shows you data nobody else can: your domain reputation as Gmail sees it (High, Medium, Low, or Bad), your spam complaint rate, and your authentication success rates.
Google publicly recommends keeping spam complaints under 0.1% and says rates above 0.3% put your mail at risk of being filtered. Postmaster Tools is where you watch that line.
Check it weekly. A reputation slide shows up here before your open rates crater, which gives you time to fix the cause instead of the symptom.
4. Check your DNS and blocklists with MXToolbox
MXToolbox is the Swiss Army knife for the technical side of deliverability.
Type in your domain and you can check your MX records, look up your SPF record, verify DKIM, inspect DMARC, and — most usefully — run a blocklist check that queries dozens of public blocklists at once to see if your domain or sending IP is listed.
Landing on a major blocklist tanks deliverability across providers. If you find a listing, don't just request delisting — find the cause first (a spam trap hit, a bounce spike, a compromised account), fix it, then request removal. Delisting without fixing the cause means relisting within weeks.
5. Read your own email headers
Free, instant, and surprisingly revealing.
Send your campaign email to your own Gmail account. Open it, click the three-dot menu, and choose "Show original." Gmail displays a summary at the top: SPF, DKIM, and DMARC, each marked pass or fail, plus which domain each check validated against.
All three should say pass, and DKIM should be signed by your own domain — not just your email tool's shared domain. Any fail here is a five-alarm finding, because mailbox providers now effectively require authentication from bulk senders. Fix the DNS records before sending another campaign.
6. Use an inbox placement service
Seed testing by hand works at small scale. Inbox placement services industrialize it.
These paid tools maintain large seed networks across dozens of providers and regions. You send to their list, and they return a placement report: what percentage of your mail hit the inbox, spam, or went missing at each provider. Many also monitor continuously and alert you when placement drops.
Worth it for high-volume senders and agencies managing multiple domains. Overkill if you send a few hundred emails a week — manual seeds plus Postmaster Tools will tell you enough.
7. Watch your campaign metrics for the pattern
Your regular sending data is a deliverability test running constantly — if you know what to read.
The signature of a deliverability problem: open rates falling across all campaigns at once (not just one bad subject line), especially concentrated at one provider. If opens from Gmail addresses collapse while Outlook holds steady, Gmail is filtering you.
Watch bounce rate hardest. Keeping bounces under 2% is the widely accepted threshold; sustained spikes above that signal list-quality problems that filters punish quickly. This is why cleaning your list matters so much — our guide to email verifier tools covers how to catch invalid addresses before they ever bounce.
What Should You Do When a Test Fails?
Work in this order — each layer depends on the one before it:
- Fix authentication first. SPF, DKIM, and DMARC must pass on your own domain. Nothing else matters until they do.
- Clean your list. Verify addresses, remove chronic non-openers, and never send to purchased lists unverified.
- Check your volume pattern. Sudden spikes from a quiet domain look like spam. Ramp up gradually, especially on new domains.
- Then look at content. Spammy phrasing, link-heavy layouts, and image-only emails hurt — but content is usually the smallest factor, not the biggest.
- Retest after every fix. One change at a time, then a fresh seed test. That's how you learn which fix actually moved the needle.
How ClickReach Approaches Deliverability
Testing tells you where you stand. Sending habits determine where you'll be next month.
ClickReach builds the protective habits into the platform: sender rotation spreads your volume across multiple inboxes so no single address sends at spam-like rates, sequences send gradually rather than in blasts, and follow-ups thread naturally like human email. It's a flat $25/month with a 15-day free trial.
Honest caveat: no sending tool can rescue a domain with broken authentication or a dirty list. Run the tests above first, fix the foundations, and then good sending habits keep you in the inbox.
Frequently Asked Questions
What is the fastest way to test email deliverability?
Send your actual campaign email to seed inboxes you control at Gmail, Outlook, and Yahoo, and note where it lands. Then send the same message to mail-tester.com for a technical score. Together the two tests take about ten minutes and reveal both the symptom (spam placement) and the likely cause (failed authentication, blocklists, or content issues).
How do I know if my emails are going to spam?
Watch for the pattern: open rates dropping across all campaigns at once, often concentrated at one provider like Gmail. Confirm with a seed test — send to your own test inboxes and see where the message lands. Check Google Postmaster Tools for your domain reputation, and run a blocklist lookup on MXToolbox to rule out listings.
Is mail-tester accurate?
Mail-tester is reliable for what it measures: authentication, blocklist status, and content scoring against spam filter rules. It cannot measure your engagement history with real recipients, which heavily influences actual inbox placement. Treat a low score as a to-do list of real problems, and a high score as necessary but not sufficient for reaching the inbox.
What is a good spam complaint rate?
Google recommends keeping spam complaints below 0.1% and warns that rates at or above 0.3% put your mail at risk of being filtered or rejected. You can monitor your actual Gmail complaint rate for free in Google Postmaster Tools. If complaints climb, tighten your targeting and make unsubscribing easier than complaining.
How often should I test email deliverability?
Run a quick seed test before every major campaign and weekly during routine sending. Check Google Postmaster Tools weekly for reputation and complaint trends. Do a deeper audit — mail-tester score, MXToolbox blocklist and DNS checks — monthly, after any DNS change, and immediately whenever open rates drop sharply without an obvious content explanation.
