Test whether email reaches inbox, spam, or promotions

MailSlurp runs seeded inbox placement tests across Gmail, Google Workspace, Outlook, Microsoft 365, Yahoo Mail, and other configured mailbox environments. Send through your real provider, then see the exact folder outcome for transactional and campaign email before customers do.

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Delivery succeeded. Placement failed.

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Placement testing explained

MailSlurp gives you a controlled seed list. You send the real message, then inspect exactly where each mailbox provider placed it.

Create a seeded test

Choose personal, business, or mixed mailbox cohorts and copy the generated target addresses and tracking token.

Send through your real provider

Send the transactional or campaign email from the domain, IP, ESP, and template you want to measure.

Review every placement

Compare inbox, Promotions, Focused, spam, junk, and missing outcomes, then repeat after each fix.

Monitor all major email services

Measure inbox, tabs, spam, junk, and missing outcomes across Gmail, Google Workspace, Outlook, Microsoft 365, Yahoo Mail, and other configured providers.

Gmail

Outlook

Yahoo

Connect with any ESP

Test the message sent through HubSpot, Mailchimp, Salesforce, Mailgun, Brevo, Campaign Monitor, or your own SMTP infrastructure.

Salesforce

HubSpot

Mailchimp

Placement health

Healthy across providers

Verify sender health

Check SPF, DKIM, DMARC, MX, blocklists, and domain changes alongside each placement result to find the cause of delivery drift.

Sender health score with SPF, DKIM, and DMARC status checks

Free spam test and inbox placement check

Send one real message and check its spam risk and inbox placement before your next campaign or product release. No signup or credit card required.

Test your email right now

Better inbox placement protects customer outcomes and revenue

When important email reaches the inbox, more customers can finish the actions that create and retain value. Measure placement alongside opens, conversions, and monthly recurring revenue to see whether email improvements support the business outcomes that matter.

More completed journeys

Keep signup, verification, checkout, and password reset messages visible.

Fewer preventable drop-offs

Catch inbox, Promotions, spam, and missing outcomes before customers do.

Stronger retention moments

Protect billing, account alert, onboarding, and lifecycle communication.

Opens and recurring revenue can move together

Illustrative correlation index, baseline = 100

Email opensMRR

Illustrative relationship, not a forecast. Actual opens and revenue depend on your audience, offer, sending program, conversion journey, and retention.

Automate seed-list placement checks from your release workflow

Create a provider cohort, send through your own SMTP or ESP, then read the placement result for each seeded account. Repeat the same check for signup, password reset, billing, alert, and lifecycle email changes.

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MailSlurp inbox placement API

const apiKey = process.env.MAILSLURP_API_KEY!;

const run = await fetch("https://api.mailslurp.com/inbox-placement-tests", {
  method: "POST",
  headers: {
    "x-api-key": apiKey,
    "content-type": "application/json",
  },
  body: JSON.stringify({
    requestedSegment: "ALL_INBOXES",
    addressFormat: "NEWLINE",
    publicShareRequested: true,
    senderDomain: "example.com",
    fromEmail: "hello@example.com",
  }),
}).then((response) => response.json());

console.log(run.seedAddresses, run.trackingToken);

Domain monitoring

Watch SPF, DKIM, DMARC, MX, blocklists, and sender-domain changes that can affect trust.

Monitor sender domains

Email audit

Inspect links, images, headers, HTML, unsubscribe support, and content warnings in the delivered email.

Audit email content

Device previews

See how the same delivered message renders across supported Gmail, Outlook, Yahoo, mobile, and desktop targets.

Preview email clients

Inbox placement testing questions

Understand where email lands, why that differs from delivery, and how to make placement checks repeatable.

What is an inbox placement test?

An inbox placement test sends a uniquely tracked email to a controlled set of seed mailboxes and records where each provider places it. Results can include the primary inbox, Focused inbox, Promotions or Updates tabs, spam or junk, quarantine, and not received. Read the inbox placement guide.

What is the difference between delivery, deliverability, and inbox placement?

Delivery means the receiving mail system accepted the message. Deliverability describes the broader ability to reach recipients successfully. Inbox placement measures the destination inside the mailbox, such as inbox, Promotions, spam, junk, or missing. A message can be delivered without reaching the inbox.

How can I test Gmail and Outlook inbox or spam placement?

Run a MailSlurp placement test against seeded mailbox cohorts that include Gmail, Google Workspace, Outlook.com, Microsoft 365, Yahoo Mail, and other configured environments. Send through your real provider, then review each provider's inbox, tab, spam, junk, or missing outcome. Run the inbox placement workflow.

How does automated seed-list inbox placement testing work?

Create a test through the MailSlurp API, choose the mailbox segment, and receive seed addresses plus a tracking token. Send through your own SMTP service or ESP with that token in the subject or body, then poll the run and results endpoints for each provider outcome. View the MailSlurp API.

When should I use a spam test, inbox placement, or sender reputation monitoring?

A spam test analyzes the message and headers for filtering risk. Inbox placement records where controlled mailbox providers actually put that email. Sender reputation monitoring watches the domain, authentication, blocklists, bounces, and other signals over time. Use all three when you need the likely reason, the observed result, and early warning of future drift. Run a free spam test.

Can MailSlurp combine placement, spam, and authentication checks?

MailSlurp combines seeded inbox placement tests, spam and content checks, delivered-email audits, and SPF, DKIM, DMARC, MX, reputation, and blocklist monitoring. The same team can compare the mailbox outcome with the message and sender evidence that explains it. Explore deliverability monitoring.

Can I test transactional email before a release?

Yes. Run placement tests for signup, verification, password reset, OTP, billing, account alert, and onboarding messages using the same sender domain, ESP, template, and authentication path planned for production. Repeat the run after a code, content, DNS, or provider change.

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