Inbox Placement Test: How to Run One, Read It by Provider and Fix Spam Placement

An inbox placement test tells you where your email actually lands: inbox, spam, a tab like Promotions, or nowhere. You send your real email to a seed list of mailboxes at Google, Microsoft and Yahoo, then read the result by provider and fix whatever pushed it to spam. For most cold email teams, a seed-list tool such as MailReach is the practical way to do it, and our MailReach review covers that tool in full.

Some tool links here are affiliate links (disclosure). Nerdy Joe is a MailReach affiliate and a PlusVibe Certified Silver Partner. Our Instantly and Smartlead links are affiliate links only, and we have no relationship with GlockApps, Mail-Tester or MXToolbox.

We did not run hands-on tests of any tool for this guide. Tool facts come from each vendor's own pages as of November 2026, vendor claims are labeled as claims, and sources are listed at the end.

What an inbox placement test is

An email can bounce, land in the inbox, or be accepted and filed somewhere the reader never looks. Most sending tools only report the first case.

A campaign can show almost no bounces while a large share of its mail sits in spam at one provider. A placement test closes that gap by checking real mailboxes and reporting what each one did with your message.

This guide covers the test itself. For how placement monitoring fits a full sending system, with warmup, daily health checks and resting weak mailboxes, see our post on mailbox warmup and inbox placement.

How seed lists work

A seed list is a set of mailboxes the testing tool controls. You send to all of them, and the tool finds your message in each one and records the folder.

Three things decide how useful a seed list is.

• Provider mix. The list should match where your recipients are. For B2B cold email that mostly means Google Workspace and Microsoft 365, with Gmail, Outlook.com and Yahoo for consumer audiences.
• Size. With only 2 or 3 mailboxes per provider, one stray result swings the percentage. More mailboxes per provider give a steadier number.
• Rotation. Some tools rotate between several seed lists so the same addresses are not tested over and over.

As one example, MailReach says its spam test sends to "30+ different mailboxes" and names Google, Microsoft and Yahoo. Its API docs describe four seed lists that can be rotated, and the score can be set to a Professional audience (Google Workspace and Microsoft 365), a Personal audience (Gmail.com, Outlook.com, Hotmail), or all of them.

The limits of a seed list

Seed mailboxes are not your prospects. They have no history with you, they do not open, reply or complain, and mailbox providers filter partly on how real recipients behave. A placement test is a sample taken under clean conditions, not a forecast for every inbox.

Seed lists also miss things. MailReach's documentation centers on Google, Microsoft and Yahoo and does not list regional providers, so check coverage if your audience uses others. A corporate mailbox behind its own security gateway can also filter differently from any seed.

How to run an inbox placement test, step by step

The steps are nearly the same in every seed-list tool. Tool-specific wording below follows MailReach's documented flow for its free test.

1. Use the real email. Take the exact message you plan to send: same subject, body, signature, links, images and tracking settings.
2. Send from the real setup. MailReach's guidance is to send the test from the same sending tool, domain and content as the real campaign.
3. Start the test and add the code. The tool gives you a short code. In MailReach's flow you paste it anywhere in the email body so the tool can find your message in each seed mailbox.
4. Send to the full seed list. Copy the list of seed addresses (MailReach lets you choose a comma, semicolon or line break separator) and send your email to all of them. MailReach says sending to the full list yourself is more reliable than tools where you send to one address that forwards the message.
5. Get the report. In MailReach you click "Get your score" to see a score, placement for each mailbox and recommendations.
6. Fix one thing and re-test. Change a single element, then test again.

If you want to try this before paying for anything, MailReach's free spam test allows up to 3 tests per 24 hours with no credit card, per MailReach. Our MailReach spam test guide walks through that tool, its score and its limits in more detail.

Run a control test alongside it

MailReach's help center recommends pairing your real email with what it calls a "100% innocent email": plain text, a neutral subject, no links, no signature and no tracking.

The pair tells you where to look. If the innocent email reaches the inbox and the real one does not, the problem is in your content, links or tracking. If both land in spam, MailReach points to the sending IP, the sending setup or a consumer-heavy audience, and the copy is not the first suspect.

How to read the results by provider

Start with the per-provider rows, not the headline score, because a blended number hides the one provider that is failing.

What each result means

• Inbox. The message landed where a person will see it.
• Spam or junk. The provider accepted the message and filtered it. This is the result to fix first.
• Categories or Promotions. The message was sorted into a tab. For a newsletter that is normal; for a one-to-one sales email it usually points to heavy formatting, images or marketing-style links.
• Missing. The message was not found in the seed mailbox. It may have been blocked or delayed, or the code may be missing from the body, so confirm the send before drawing conclusions.

Professional vs personal results

These two groups often disagree. MailReach notes that professional inboxes can show 100% inbox placement while personal inboxes still filter the same email to spam.

So score yourself against the audience you actually email. A B2B sender should weigh Google Workspace and Microsoft 365 most heavily.

What counts as a good result

There is no official pass mark. MailReach says a 90% or higher inbox placement rate is considered strong, and the system described in our warmup and placement post also treats 90% per provider as its health line.

On scores: MailReach's free tool describes its score out of 10, while its API returns a 0 to 100 score. MailReach also says 10 out of 10 is not always achievable for some email types, so chase the per-provider placement, not a perfect number.

How often to run an inbox placement test

MailReach's own guidance is simple: re-test when content, links, images or sending setup change, and you do not need a separate test per country. Building on that, a sensible schedule looks like this.

The last row is our suggestion, not a published rule, and the right frequency depends on how many mailboxes you run.

Paid tools can automate this. MailReach's paid Spam Tester lists automated tests at a chosen frequency with Slack and webhook alerts, plus test history. The frequency options and how automated runs use credits are not documented on the pages we read, so confirm that in the app.

Common causes of spam placement and how to fix them

Work through these in order, since the early ones are cheap to check.

Links and tracking

MailReach's help center says that "in 80% of cases" where a sender has a high reputation score and still lands in spam, the cause is links and tracking without a custom tracking domain. That is MailReach's claim, with no published data behind it, but the control test will confirm or rule it out for your email.

Reputation and volume

Google's sender guidelines ask senders to keep spam rates reported in Postmaster Tools below 0.10%, avoid ever reaching 0.30%, and increase sending volume slowly. Yahoo asks senders to keep their spam rate below 0.3%. A placement test does not show complaint rates, so check them separately when placement falls on every email you test.

MailReach's guidance for a reputation drop is to cut or pause campaign sending first, keep bounces under 5%, limit follow-ups, and only then raise warmup volume. It also says plainly that warmup "can't magically fix bad sending practices." For setup basics, see our cold email infrastructure guide.

Inbox placement test tools compared

Prices and limits below are from each vendor's site as of November 2026 unless a different date is shown.

Notes on the table

MailReach. In MailReach, 1 credit is 1 placement test with a report. The 200 credit price works out to $1.05 per test by our arithmetic. MailReach's own blog posts cite a starting price for the standalone Spam Tester of between $15 and $19.50 a month, and they disagree with each other, so check the pricing slider; our MailReach pricing breakdown lists what is and is not published.

GlockApps. Its credit allowances are much larger for the price, bundled with DMARC analytics and monitors. Its pricing page did not show seed list size or providers when we read it, and no warmup feature is listed there.

Mail-Tester. It scores one message out of 10 using a SpamAssassin-based check of the message, sending server and IP. It does not show where mail lands at Google, Microsoft or Yahoo, so treat it as a pre-check.

Google Postmaster Tools. It shows Google's own data on your domain: spam rate, reputation, authentication and delivery errors. It covers personal Gmail accounts only, and Google says data may be missing on low-volume days.

For a wider look at standalone warmup tools, see our roundup of the best email warmup tools.

What an inbox placement test cannot tell you

A good result is permission to send, not proof the campaign will work. It does not measure your list: an email that inboxes at every seed will still hurt your domain if it goes to unverified addresses or to people with no reason to hear from you.

One test is also one moment, which is why the schedule matters more than any single score.

Inbox placement test checklist

• [ ] SPF, DKIM and DMARC are published and pass
• [ ] The test uses the real subject, body, signature, links and tracking
• [ ] The test is sent from the real sending tool, domain and mailbox
• [ ] The test code is in the body and the email went to the full seed list
• [ ] A plain "innocent" control email was tested alongside the real one
• [ ] Results were read by provider, with professional and personal inboxes separated
• [ ] A re-test is planned for every change to copy, links, images or setup

Rather not build the list yourself?

Placement testing, warmup, list verification and daily mailbox checks add up to real weekly work. Nerdy Joe is owned by Agency Growth Partners (AGP), and AGP builds verified lists and runs outbound for agencies.

If you would rather hand that off, book a call with David.

Bottom line

An inbox placement test is the only pre-send way to see where your email lands at each provider. Run it with the real email from the real setup, pair it with a plain control email, read the result per provider, and re-test after every change.

To start free, run a MailReach spam test on your next campaign email. Before you pay for credits or warmup, read the full MailReach review for pricing, limits and the cases where another tool fits better.

Disclosure: My relationship with Instantly is that of an independent party. I do not hold any position, nor do I have the power to form binding agreements or act on behalf of Instantly. My earnings are derived from referral compensations provided by Instantly. The views I share are solely mine and should not be seen as official statements, promises, or representations of Instantly, or any related entities or personnel.

Sources

• MailReach: Email spam test
• MailReach: Email deliverability test
• MailReach: Pricing
• MailReach API docs: Spam test
• MailReach: Email spam test API
• MailReach blog: Email spam test tools
• MailReach blog: Folderly pricing
• MailReach Help: Why am I still landing in spam with a high reputation score
• MailReach Help: How to help fix a spam spike or reputation score drop
• MailReach Help: How to restore a bad sender reputation
• Gmail Help: Email sender guidelines
• Google Workspace Admin Help: Postmaster Tools
• Yahoo Sender Hub: Sender best practices
• GlockApps pricing
• Mail-Tester
• Mail-Tester FAQ
• Mail-Tester account plans
• MXToolbox Delivery Center
• Instantly pricing
• Smartlead pricing
• PlusVibe pricing