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Best inbox placement testing tools (2026): what we use, and how to read the results

Inbox placement testing tools send your email to a list of seed mailboxes at Gmail, Outlook, Yahoo and other providers, then report whether each copy landed in the inbox, the spam folder, or a tab like Promotions. It is the only way to see where cold email lands before the reply rate tells you, weeks late.

Below is what OneGTM uses, then the dedicated seed testers and the free checks worth running, with what each vendor publishes about price. Some links are referral links that may earn us a credit, which never changes what you pay or who is listed. Run DNS checks first with our free deliverability checker. A placement test on a domain with broken DMARC just tells you what you already should have fixed.

By Garrett Wolfe, founder of OneGTM (Clay Artisan Solutions Partner) and former GTM engineer at Unify. Updated .

Key takeaways

  • We run placement tests inside Instantly, the same tool that sends and warms our ScaledMail inboxes.
  • GlockApps, EmailGuard and Smartlead SmartDelivery are the main standalone seed testers, from about $49 a month.
  • Mail-tester, Google Postmaster Tools and Microsoft SNDS are free, and each answers a narrower question.
  • Seed tests are a smoke alarm. A bad result is worth acting on; a good one does not prove real buyers see your email.
  • Test the real copy from the real mailbox through the real sequencer, or the result means little.

What OneGTM uses

Our mailboxes come from ScaledMail and send through Instantly, so we test placement inside Instantly too. The test goes out from the same connected accounts and campaigns that send to prospects, which keeps the result close to what a real recipient gets. Infrastructure choices are covered in cold email infrastructure and warmup in email warmup tools.

Instantly

OneGTM uses this

Inbox placement tests built into the sequencer. Tests send from your connected accounts to seed addresses at Gmail, Outlook, Yahoo and other providers, show folder placement per provider, and can run on a schedule with alerts when an account starts landing in spam.

Best for: Testing the mailboxes and campaigns you already send from

Pricing: 2 free tests to start. Unlimited one-time tests on the Growth plan ($47/month) and unlimited automated tests on Hypergrowth ($97/month).

Dedicated inbox placement testers

These run seed list tests on their own, outside your sequencer. Most bundle placement tests with blacklist monitoring, DMARC reports, or warmup, and sell tests as monthly credits.

GlockApps

Long-running seed list tester that shows inbox, spam and tab placement across providers, with authentication checks, DMARC report analysis, IP reputation monitors and uptime monitors in the same account.

Best for: A standalone tester with DMARC reports included

Pricing: Free plan with 2 spam test credits. Essential $59/month (360 credits), Growth $99/month (1,080 credits), Enterprise $129/month (1,800 credits). Custom plans for large senders.

EmailGuard

Deliverability toolkit built for cold email teams: inbox placement tests, spam filter tests, content spam checks, blacklist monitoring, DMARC monitoring, and hosted redirect domains for tracking links.

Best for: Cold email agencies testing many domains

Pricing: Free plan (1 domain, 10 spam filter tests). Pro $49/month (300 inbox placement tests), Business $129/month (500), Agencies $199/month (1,500). Custom plans on request.

Smartlead SmartDelivery

Smartlead's placement testing product. It tests whole campaign sequences across many sender accounts at once, and the higher tiers add placement-tuned copy suggestions and API access.

Best for: Teams sending through Smartlead

Pricing: Growth $49/month (120 sequence tests, up to 50 sender accounts per test); Pro $174/month (unlimited tests, up to 200 accounts); Expert $599/month (up to 500 accounts).

MailReach

Warmup service that also sells spam test credits. Each credit runs one placement test with a deliverability report, and a free spam test is available on the site.

Best for: Warming a few mailboxes and testing them in one place

Pricing: Warmup $19.50 per mailbox per month, including at least 20 spam test credits. Standalone test credit packs are priced by volume on the site's calculator.

Folderly Inbox Insights

Folderly's placement testing product, sold separately from its managed deliverability service. Free monitoring alerts come with it through Folderly Pulse.

Best for: A low-volume monthly test with a free tier

Pricing: Free with 2 tests a month; $79/month for 100 tests a month, or $799 billed yearly. Folderly's core deliverability service is $96 per mailbox per month billed yearly.

Warmy

Warmup platform with placement test credits and a rotating US seed list of more than 500,000 mailboxes, plus a deliverability tester for authentication and blacklist checks.

Best for: Large seed lists bundled with warmup

Pricing: Plans start from $49/month, priced by warmup volume. Test credit allowance is set per plan by the Warmy team. 7-day free trial.

lemlist

Sequencer with a deliverability hub included on every plan: lemwarm warmup, deliverability testing, a DNS setup test, and deliverability alerts.

Best for: Teams already sending through lemlist

Pricing: Email $69/month ($55/month billed yearly); Multichannel $109/month ($87/month billed yearly). Deliverability tools included on all plans.

Validity Engage

Validity's enterprise deliverability platform (the old Everest product page now describes Engage), with real-time placement testing across major providers built on the Validity Intelligence Network.

Best for: High-volume marketing senders

Pricing: Custom pricing based on sending volume, domains, IPs, features and team size.

Free checks to run alongside a seed test

None of these is a full seed list test. Each one answers a narrower question for free, and together they catch most problems before you pay for credits.

Mail-tester

Send one email to a throwaway address and get a score out of 10 covering SPF, DKIM, DMARC, blacklists and spammy content. It does not show which folder you land in at each provider.

Best for: A quick content and authentication score

Pricing: Occasional manual tests free with no account. Subscriptions from $10/month for 50 tests to $250/month for 7,500; one-time packs from $5 for 10 tests.

Google Postmaster Tools

Google's own dashboards for spam rate, reputation, authentication and delivery errors on mail sent to Gmail addresses from a domain you verify. Data only shows once daily volume to Gmail is high enough.

Best for: Watching your spam rate at Gmail

Pricing: Free with a Google account.

Microsoft SNDS

Microsoft's Smart Network Data Services shows complaint rates and spam trap hits for IP addresses you control, for mail sent to Outlook.com and Hotmail. Teams sending from Google Workspace or Microsoft 365 mailboxes do not own their IPs and will get little from it.

Best for: Senders on their own dedicated IPs

Pricing: Free.

Prices are from each vendor's site as of October 2026 and change often, so check before you buy. This is an opinionated list, not a paid ranking. Some links are referral links that may earn us a credit; that never changes what you pay or who makes the list.

Inbox placement testing tools compared

ToolBest forStarting price
Instantly (OneGTM uses)Testing the mailboxes and campaigns you already send fromIncluded from $47/month
GlockAppsA standalone tester with DMARC reports includedFree; Essential $59/month
EmailGuardCold email agencies testing many domainsFree; Pro $49/month
Smartlead SmartDeliveryTeams sending through SmartleadFrom $49/month
MailReachWarming a few mailboxes and testing them in one place$19.50/mailbox/month
Folderly Inbox InsightsA low-volume monthly test with a free tierFree; $79/month for 100 tests
WarmyLarge seed lists bundled with warmupFrom $49/month
lemlistTeams already sending through lemlistFrom $55/month billed yearly
Validity EngageHigh-volume marketing sendersCustom pricing
Mail-testerA quick content and authentication scoreFree; packs from $5
Google Postmaster ToolsWatching your spam rate at GmailFree
Microsoft SNDSSenders on their own dedicated IPsFree

Starting prices as published by each vendor in October 2026.

How seed tests work, and where they mislead

A seed test sends your email to a fixed list of mailboxes the vendor controls and checks which folder each copy lands in. The result is a percentage: so much inbox, so much spam, so much missing.

Seed mailboxes are not your buyers. Gmail and Outlook filter per recipient, and a seed account that never opens or replies gets treated differently from a VP who has emailed your domain before. Corporate filters such as Proofpoint and Mimecast sit in front of many B2B inboxes, and most seed lists only partly cover them. Read a bad result as a real warning. Read a good result as "nothing obviously broken", nothing more.

How to run a placement test that means something

Most bad tests come from testing something other than what you actually send. Send the test the same way a prospect gets the email.

  • Send from the actual mailbox, through the sequencer, not from your personal inbox.
  • Use the real copy, with the real links and tracking settings. Tracking domains and link shorteners change results.
  • Test a sample of mailboxes on each domain, since reputation sits on both the mailbox and the domain.
  • Retest after any change to copy, tracking, DNS or daily volume, and on a schedule once campaigns are live.
  • Compare results over time for the same mailbox. One test on one day is noisy.

What to do when a test lands in spam

Stop sending from the affected mailboxes first. Every email that lands in spam while you investigate makes the reputation worse.

Then work from the cheap fixes to the expensive ones. Check SPF, DKIM and DMARC with the deliverability checker. Strip links, images and tracking from the copy and test again. Cut daily volume per mailbox. If the domain still fails after a couple of weeks of warmup only, retire it and move to fresh domains on separate infrastructure. Also check your list. Bounces from unverified emails hurt placement more than most copy problems, which is why every list we send gets run through email verification first.

When to get help with deliverability

Running a placement test takes five minutes. Knowing which of a dozen causes is behind a bad result, and fixing it without burning more domains, is the slow part.

OneGTM sets up the mailboxes, DNS, warmup and testing for client sending, and builds the monitoring that flags a mailbox before reply rates drop. You own the domains, accounts and data.

  • Reply rates fell and you suspect spam placement.
  • Placement tests come back mixed and you cannot tell why.
  • You are moving to new domains and want them set up right the first time.
  • You send from dozens of mailboxes and nobody checks placement.

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Inbox placement testing FAQ

What are the best inbox placement testing tools?
For cold email, the best inbox placement testing tool is usually the one inside your sequencer, because it tests the mailboxes and copy you actually send. OneGTM uses Instantly's placement tests. GlockApps and EmailGuard are the strongest standalone testers, and Smartlead SmartDelivery suits teams on Smartlead.
What is an inbox placement test?
An inbox placement test sends your email to seed mailboxes at Gmail, Outlook, Yahoo and other providers and reports which folder each copy reached: inbox, spam, a tab, or missing. Tools like GlockApps, EmailGuard and Instantly run them.
Is there a free inbox placement test?
Yes. Instantly gives 2 free tests, GlockApps includes 2 spam test credits on its free plan, and Folderly Inbox Insights has 2 free tests a month. Mail-tester is free for occasional use but scores content and authentication rather than folder placement.
Are seed list tests accurate?
Seed list tests are accurate about the seed mailboxes and only roughly predictive for real recipients. Gmail and Outlook filter per user, and corporate filters often sit in front of B2B inboxes. Treat a spam result as a real problem and a clean result as a sign nothing is obviously broken.
What is the difference between Mail-tester and an inbox placement test?
Mail-tester sends one email to one address and scores your authentication, blacklist status and content out of 10. An inbox placement test from GlockApps, EmailGuard or Instantly sends to many seed mailboxes across providers and shows which folder you land in at each one.
Should I use Google Postmaster Tools for cold email?
Yes, set up Google Postmaster Tools on every sending domain. It is free and shows your spam rate and reputation at Gmail, though data only appears once you send enough daily volume to Gmail addresses. Microsoft SNDS only helps if you control your own sending IPs.
How often should I run inbox placement tests?
Run an inbox placement test before a new domain or campaign goes live, after any change to copy, tracking or DNS, and on a regular schedule while campaigns are sending. Instantly's Hypergrowth plan and GlockApps can automate recurring tests.

Not sure where your cold email is landing?

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