Email deliverability test for cold email: how to check inbox placement

An email deliverability test sends a real message to accounts you control and reports which folder or tab it landed in, so you can see where your cold email actually goes before a prospect ever does. For cold outreach, that test matters more than for a newsletter, because the message has no opt-in and no reader history to fall back on.

This page covers the specific tests worth running, what each one can and cannot tell you, and the formula behind inbox placement rate. For the wider picture of what drives cold email into spam, start with our cold email deliverability guide.

What is an email deliverability test for cold email?

An email deliverability test checks where a cold email lands: the inbox, a tab like Promotions, or spam. It is a measurement, not a fix, and it only tells you about the moment it ran.

Most tools that rank for "email deliverability test" are built for newsletters: lists of opted-in subscribers, sent from one long-running domain. Cold email is a harder case. There is no opt-in, no existing relationship, and often a brand-new sending domain, so the same test carries more weight. A single clean result on a newsletter domain means less than the same result on a cold email domain that started sending last week.

How do seed list placement tests work for cold email?

A seed list placement test sends your real email to a set of accounts at Gmail, Outlook and other providers that the testing service controls, then reports back which folder or tab each one landed in. It is the closest thing to watching a prospect's inbox without being the prospect.

A seed test is only as good as how it reads the result:

1. Read provider labels, not just folders. A tool that only checks folders over IMAP can count a Gmail Promotions message as "inbox", because Promotions mail also carries the inbox label. A trustworthy seed test reads Gmail's category label.
2. Use more than a handful of seed accounts. A result from three accounts can flip on one filter quirk, so treat a small seed list as a hint, not a verdict.
3. Compare providers separately, not as one blended score. Gmail, Outlook.com and Microsoft 365 run separate spam filters, so a 90% average can hide one provider filtering everything.
4. Read the result against the mailbox's history. A test on a domain's first day measures something different from the same test after two weeks of warm-up.

The limit to know before you lean on this test: seed accounts are not real prospects. They have no history of opening, replying to or searching for mail from people like you, so they lack the engagement signal that providers increasingly use to personalize filtering.

A seed account can show inbox placement that a real, cold recipient at the same provider does not get, and the reverse is also possible. Treat a seed test as a useful early check on authentication and obvious spam triggers, not as a promise about every real inbox.

How do you check cold email deliverability with Gmail's header check?

Check email deliverability for free by sending one email to a Gmail account you own, opening it, and choosing "Show original." Gmail shows whether SPF, DKIM and DMARC each passed, right in the raw headers.

This is the cheapest test that exists and the one to run first on any new domain:

1. Send a real email to a Gmail address you control.
2. Open it in Gmail and click the three dots, then "Show original."
3. Look for SPF: PASS, DKIM: PASS and DMARC: PASS. Anything else means fix that before testing anything further.

A header check answers a narrow question: did this one message pass authentication right now. It says nothing about spam complaints, volume patterns or where a hundred other messages landed. It is a precondition for good placement, not a measure of it. Our page on why cold emails go to spam covers the other five causes a header check cannot see.

Can warm-up placement rate work as an ongoing cold email deliverability test?

Yes. A warm-up tool that reports where its own daily mail lands gives you a running deliverability test for free, before a single cold email goes out and for as long as the mailbox keeps sending. It will not predict every real prospect's filter, but a mailbox whose warm-up mail is sliding toward spam is a mailbox you should not be sending cold email from, full stop.

This is how Pipefire uses that signal on every mailbox it runs. A mailbox is held out of cold sending until its warm-up mail stays under a 10% spam rate across at least 20 warm-up emails measured over the trailing 7 days.

A mailbox already sending cold email that slides to a 20% warm-up spam rate over the same window is pulled back off cold sending automatically. It returns to warm-up and restarts cold volume at about 5 a day once it recovers. Our email warm-up guide explains the full schedule this check sits inside.

Treat this as what it is: a test of warm-up traffic between mailboxes designed to look like normal mail, run continuously. It is a strong early warning and a useful gate, but it is still not the same measurement as sending your actual cold email to a real stranger's inbox.

Does Google Postmaster Tools test cold email deliverability?

Google Postmaster Tools reports Gmail-specific signals, including spam rate and authentication compliance, for domains sending enough mail to personal Gmail accounts. It is free and worth setting up, but it is not built around any single send the way a placement test is.

Two live limits matter for a cold email setup. Both are worth checking against Google's current documentation before you rely on them, since Google has changed this product recently:

• Low-volume domains see blank data. Google suppresses dashboard data on low-volume days for privacy. A new domain sending a modest volume can show nothing for weeks. A blank chart is not a clean result, it is an absence of data.
• Domain and IP Reputation are gone from v2. Google says the new Postmaster Tools (v2) drops the Domain and IP Reputation dashboards, replacing them with Compliance status and Spam rate views. Google also postponed retiring the old v1 interface without naming a new date, so both versions are live for now. See Google's notice on the change before trusting an older guide that still talks about a reputation score.

Postmaster Tools is a good complement to a placement test, not a replacement. It can confirm your spam complaint rate and authentication status at scale, long after a seed test on a handful of accounts has already told you something is wrong.

How do you calculate inbox placement rate for cold email?

Inbox placement rate is the share of a test send that landed in the primary inbox, calculated as inbox placements divided by total messages sent to the test accounts, times 100.

The formula is: inbox placement rate as a percent equals messages landing in the inbox, divided by total messages sent, multiplied by 100.

Here is a worked example using invented numbers, not a Pipefire result. Say a seed list test sends to 50 accounts across Gmail, Outlook and Yahoo. 38 land in the primary inbox, 7 land in Gmail's Promotions tab, 3 land in spam, and 2 never arrive. Inbox placement rate works out to 38 divided by 50, times 100, which is 76%.

Whether Promotions counts as a win depends on what you are measuring for. For a newsletter, Promotions is often treated as a pass, since subscribers browse that tab. For cold email, a prospect who did not ask for your message is unlikely to check it. A more honest version weights Promotions, Updates and Social mostly as losses. A rate built only from "landed somewhere in Gmail" overstates how many prospects see your message.

Our inbox placement guide covers why publishers disagree on the formula and why a seed test is only an estimate.

How often should you run a cold email deliverability test?

Run a deliverability test on every new sending domain before it starts cold sending, then again after any change: a new DNS record, a volume increase, a new list, or new email copy. Outside of changes, a light recheck every few weeks catches slow reputation drift.

A sensible minimum schedule:

1. Before first cold send. Header check at minimum, plus a seed test if you have one.
2. After any DNS or authentication change. A broken SPF or DKIM record can pass silently until the next real test.
3. After a volume increase. Ramping a mailbox's daily cap changes placement.
4. Every 2 to 4 weeks on active domains. Reputation can slide gradually with no single trigger. This is what an ongoing warm-up placement check is for.

One test is a photograph, not a trend line. The value comes from testing the same way, often enough, to notice when the picture changes.

Pipefire warms every mailbox for at least 14 days and holds it out of cold sending until its warm-up placement rate clears that bar, then keeps checking the same number every day a mailbox sends cold email. Our deliverability page shows the other thresholds it enforces automatically, for bounces and spam complaints.

Cold email deliverability test FAQ

What is the best free way to test cold email deliverability?

Send one email to a Gmail account you own and choose "Show original" to check SPF, DKIM and DMARC. It costs nothing, takes a minute, and catches the most common cause of cold email landing in spam: broken authentication.

How do I check cold email deliverability in Gmail specifically?

Open the message and click the three dots in the top right, then choose "Show original." The authentication results appear near the top of the raw message. The Gmail account itself also shows whether the message sat in the inbox or a tab.

What is a good inbox placement rate for cold email?

There is no single published benchmark for cold email specifically, since cold outreach has no opt-in to compare against newsletter data. Aim for the large majority of test sends landing in the primary inbox, and treat anything landing in Promotions, Updates or Social as mostly lost for a one-to-one cold message.

Why does a deliverability test show 100% inbox when my cold email campaign still goes to spam?

Tests that only send between your own mailboxes almost always show perfect placement, because your own setup already trusts itself. That result says nothing about how a stranger's Gmail or Outlook account, with no relationship to you, will treat the same message.

Do seed list tests work for cold email the same way they work for newsletters?

Not exactly. Seed accounts lack the open, reply and search history that providers increasingly use to personalize filtering for real subscribers, so a seed result is a useful signal rather than a guarantee. It is still the most direct test available short of emailing real prospects.