Email Deliverability Testing
Send one campaign to a seed list of real mailboxes at 6 major providers and get a spam placement report in under 5 minutes: primary inbox, promotions tab, spam folder, or missing entirely. Test email deliverability before the real send, not after the open rates crater.
87%
Avg Inbox
8%
Spam
5%
Missing
6 major providers · Content analysis · Results in under 5 minutes
Trusted by 500,000+ leading GTM teams of all sizes
Seed lists, explained
An inbox placement test answers the one question your ESP dashboard cannot: of the emails marked “delivered,” how many were actually seen? Delivered only means a receiving server accepted the message. It says nothing about whether Gmail filed it under Promotions, Outlook quarantined it, or Yahoo dropped it into spam where it will never be opened. The test works by seeding: you send one campaign to a list of real, monitored mailboxes spread across 6 major providers, and Verifox checks each mailbox and records the exact folder. The result is a per-provider placement report, inbox versus spam versus missing, in under 5 minutes.
Per-provider matters because there is no single spam filter. Gmail leans on engagement history and tab classification, Outlook runs SmartScreen against reputation databases, Yahoo weighs complaint feedback loops, and Apple Mail leans on authentication because Mail Privacy Protection hides opens. The same email routinely scores 95% inbox at one provider and 60% at another, and a blended average hides exactly the provider that is bleeding. Placement also depends on signals a content edit cannot fix: if SPF, DKIM, or DMARC fails, run the DMARC, DKIM, and SPF check and a full deliverability test before blaming the subject line.
The third input is the list itself. Hard bounces and spam-trap hits from a stale list drag down the sender reputation every future send inherits, and 20 to 40% of B2B lists fail at catch-all domains, the check most free tools skip. The 9-point email verification engine removes those addresses before they poison your placement, and a cold domain should finish email warmup before its first real campaign. Test, fix, retest: that loop is the whole discipline.
Sample placement report
Each bar shows the share of seed addresses that received the email in the inbox, the spam folder, or not at all. Real mailboxes at each provider, checked one by one. No simulated filters, no blended score.
Gmail
92%
Outlook
84%
Yahoo
88%
Apple Mail
95%
AOL
79%
Google Workspace
90%
Before you blame the inbox
Every test email is scanned for the content signals provider filters score hardest. Fix the warnings here before they cost you inbox placement on the real send.
Email Preview: Content Analysis
Subject Line
“Your March report is ready”
No spam trigger words detected
HTML Ratio
Hi Alex, here is your monthly deliverability report. Open rates improved by 12% this quarter…
Text-to-HTML ratio within range
Image Weight
chart-march.png
680 KB · 48% of body weight
Link Count
View full report · Update preferences
Under 5 unique domains linked
Unsubscribe Header
Unsubscribe· Verifox Inc, 123 Market St
List-Unsubscribe header present
Spam Score
SpamAssassin: 4.2 / 5.0
Flagged image weight and subject-to-body ratio
4 passed · 2 warnings
Fix image weight before sending
Real seed addresses · Not simulated · Actual provider behavior
Three steps, five minutes
01
Send to the seed list
We give you a unique seed list of real addresses across 6 major providers. Send your campaign to that list exactly as you would to your real subscribers.
02
We check every mailbox
Within minutes, our system logs into each seed mailbox and records where your email landed: primary inbox, promotions tab, spam folder, or missing entirely.
03
Review and fix
Get a per-provider breakdown with content analysis. See exactly what to change in your email before you send to your full list.
Three tests, three jobs
The names get used interchangeably, but each test answers a different question. Use the spam content checker while drafting, the deliverability tester to audit your setup, and the placement test to verify the result.
Answers "where did this exact email land, at each provider?" by sending to real seed mailboxes and checking every folder. The only test that measures the outcome itself rather than the inputs to it.
Audits the inputs: DNS records, SPF, DKIM, DMARC, blacklist status, server configuration. It predicts trouble but never opens a mailbox to confirm where mail actually arrives.
Scores the message body alone against filter rules and trigger words. Useful while drafting, but blind to sender reputation, authentication, and the per-provider behavior that decides placement.
Answers "where did this exact email land, at each provider?" by sending to real seed mailboxes and checking every folder. The only test that measures the outcome itself rather than the inputs to it.
Audits the inputs: DNS records, SPF, DKIM, DMARC, blacklist status, server configuration. It predicts trouble but never opens a mailbox to confirm where mail actually arrives.
Scores the message body alone against filter rules and trigger words. Useful while drafting, but blind to sender reputation, authentication, and the per-provider behavior that decides placement.
Timing the test
01
A placement test costs minutes; a campaign that lands 30% in spam costs the list. Test the final draft, from the actual sending domain, before the real send goes out.
02
New HTML structure, a new sending IP, or a fresh subdomain all reset how filters see you. Anything that changes the fingerprint of your mail deserves a fresh test.
03
A placement test is the graduation exam for domain warming. Run one before the ramp and one after, and you have before-and-after proof the reputation actually moved.
04
A sudden open-rate cliff usually means a provider started filing you under spam or Promotions. A placement test tells you which provider, and which folder, within minutes.
Trust & compliance
Every layer of the stack carries a third-party attestation, so you can ship into regulated industries without rebuilding your compliance posture.
Independently audited to the SOC 2 Type II standard.
Built for the EU with full GDPR data-subject rights.
California opt-out, do-not-sell, plus DSAR handling.
Information security held to the ISO 27001 standard.
AI governance aligned to the new ISO 42001 standard.
Before you seed
How seed lists work, whether Promotions counts as a loss, how predictive the results are, and what to fix first when the report comes back red. Real numbers, no hedging.
An inbox placement test sends your email to a seed list of real mailboxes at major providers, then checks each one to record where the message landed: primary inbox, Promotions tab, spam folder, or nowhere at all. It measures the actual outcome of a send, per provider, instead of inferring it from open rates after the damage is done. Verifox covers 6 providers and returns the report in under 5 minutes.
A seed list is a set of real, monitored email addresses spread across Gmail, Outlook, Yahoo, Apple Mail, AOL, and Google Workspace. You add those addresses to your send exactly as if they were subscribers. Our system then opens each seed mailbox and logs the folder your email arrived in. Nothing is simulated: the message travels through the same filters your real subscribers’ mail does.
No. Promotions is still the inbox; subscribers see it, and engaged readers open it. Spam is invisible by default and actively damages sender reputation when messages sit unread. Treat Promotions as a tab-optimization problem (fewer images, fewer links, more personal tone) and spam as an emergency. If your mail sits in spam at multiple providers, start with email warmup and authentication, not subject-line tweaks.
A placement test measures the outcome: it checks real mailboxes and reports the folder your email landed in at each provider. A deliverability test audits the inputs: DNS, authentication, blacklist status, server setup. A spam check scores the message content alone. Run the input tests to find what to fix, then the placement test to confirm the fix worked.
Directionally, yes; exactly, no. Seed mailboxes share your real subscribers’ filters but not their engagement history, so an address that opens you weekly will place slightly better than the seed result, and a dead list will place worse. The biggest gap comes from list quality itself: 20 to 40% of B2B lists fail at catch-all domains. Clean the list with email verification before reading too much into either number.
Six: Gmail, Outlook, Yahoo, Apple Mail, AOL, and Google Workspace. Consumer Gmail and Google Workspace are tracked separately because their filtering behaves differently; Workspace admins layer custom rules on top of Google’s defaults. Each provider’s result shows inbox, spam, and missing percentages plus tab placement where the provider has tabs, so you see exactly which audience segment is at risk.
Authentication, then reputation, then content, in that order. Confirm SPF, DKIM, and DMARC all pass with the DMARC, DKIM, and SPF checker; unauthenticated mail loses before content is even read. Next, check whether your domain or IP is listed with the domain spam checker or blacklist check. Only then rework the content warnings from the placement report.
Before every major campaign at minimum, and monthly as a baseline even when nothing changes, because provider filters update quietly and placement drifts without warning. Add an extra test after any change to your template, sending domain, or ESP. Teams on pay-as-you-go credits typically budget a handful of tests per month per sending domain; credits never expire, so an unused month is never wasted.
Yes. Signing up is free, takes no card, and includes 1,000 credits, or 2,500 if you register with a work address. That covers your first placement tests plus enough verification to clean the list you are about to send to. When you outgrow the free credits, volume pricing is shown for your region on the pricing page.
Yes. Every test can be triggered and collected over REST, so you can run a placement check as a pre-send gate in your campaign pipeline and fail the deploy if inbox rate drops below your threshold. Endpoint shapes and auth are in the API docs. AI agents can drive the same engine through the native MCP server with no glue code.
Sign up free, grab your seed list, and run your first inbox placement test today: per-provider results across 6 providers in under 5 minutes, content warnings included. Signup brings 1,000 free credits, 2,500 with a work email, enough to test the campaign and verify the list it is going to. No card required, and credits never expire.
6 providers · Results in under 5 minutes · No card required
