Email deliverability test
An email deliverability test sends a message to controlled addresses and reports where it landed and what about the sender's setup or content could get it filtered.
Also called Deliverability check, Inbox placement test, Spam test.
An email deliverability test finds out where your email lands before your prospects do. You send a message to an address the testing service controls, or to seed mailboxes at Gmail, Outlook and Yahoo, and it reports what it saw: whether the message arrived, which folder it went to, and what about your setup or content a filter might hold against you.
The checks fall into four groups. Authentication: whether SPF, DKIM and DMARC records exist and pass for the message you sent. Reputation: whether the domain or IP is on a public blocklist such as Spamhaus. Content: HTML weight, broken links, a missing unsubscribe and the words older filters score against. Placement: for a seed-list test, which folder the message landed in at each provider.
The two kinds answer different questions. A one-off check, of the kind mail-tester.com or MXToolbox run, grades the technical setup around a single message. A seed-list placement test, which several paid services offer, sends the same message to dozens of real mailboxes across providers and reports what share reached the inbox. The first checks your plumbing; the second samples the outcome.
How to test email deliverability
- Send the real message: the account, the domain and the exact copy you plan to send, unsubscribe line included, because a filter grades the whole thing together.
- Check authentication first. A failing SPF, DKIM or DMARC record explains most bad results on its own and is fixed in DNS rather than in the copy.
- Look up the domain and IP on the public blocklists. A listing has to be cleared first; no change to the copy will get past it.
- Read the content flags with some scepticism. Filters weigh sender history far above wording, so a "spammy word" warning is a low priority next to a missing record.
- If you run a placement test, send to seeds at the providers your prospects use. Business mailboxes are usually Google Workspace or Microsoft 365, and a result for Yahoo says little about that audience.
- Run it again when something changes: a new domain, a new sending tool, a DNS edit, or a sudden fall in replies. Otherwise once a month is plenty.
- On a bad result, fix the records, get off any blocklist, then lower volume rather than pushing through. A domain that keeps sending into spam confirms the filter's judgement.
What a test cannot tell you
A test sees a snapshot from mailboxes that are not your prospects'. Their filters have a history with you that a seed account does not: how that company's people treated your earlier mail, and what the rest of your domain has been sending for months. A clean result on day one of a new domain is the least informative there is, because nobody has any history to judge yet. A test cannot show reputation over time, which is what actually decides placement, and it cannot tell you whether anyone read the message. It tells you the plumbing is sound, which is necessary and is not the same as the message being welcome.
What Kamu records instead
Kamu does not run placement tests. It records what the receiving server said about every email it actually sent, delivered, bounced, marked as spam or failed, from the sending provider's own events. That answers a different question, whether the mail you are really sending to the people you are really writing to is arriving, and it answers it continuously rather than once. A test before the first send is still worth doing; the two are not substitutes.
In practice
- A one-off check that returns a low score because DMARC is missing, fixed by adding one DNS record.
- A seed-list test showing the same message in the inbox at Gmail and in junk at Outlook, pointing at a reputation gap rather than a content problem.
- A perfect score on a fresh domain, followed a week later by real mail landing in spam once volume started.
Questions
How do I test email deliverability for free?
Send a message to a free one-off checker such as mail-tester.com, and look up the sending domain and IP with MXToolbox. Between them you get the authentication results, blocklist status and the content flags. What neither gives you for free is a placement sample across many real mailboxes, which is the part the paid seed-list services charge for. For a small sender the free checks catch most of what goes wrong.
How often should I run a deliverability test?
Whenever something about the sending setup changes, and otherwise roughly monthly. A new domain, a new tool, a DNS change, a new template or a sudden drop in replies are all reasons to test now. A domain sending steadily, with low bounces and replies coming in, is passing a live test every day, and the formal one adds little.
Why does my test pass but my emails still land in spam?
Because the test sees a mailbox with no history of you and your prospects' mailboxes have one. Reputation is built per receiving provider from how its users treated your earlier mail, and a seed account has none of that. A passing test rules out the mechanical problems, which is useful. What remains is how you have been sending: volume on a young domain, bounces, complaints, and whether anyone replies.
What is a good email deliverability test score?
The scores are each tool's own scale and are not comparable between tools. A score at the top of the scale means the mechanical checks came back clean, and that is the useful reading: what was flagged, rather than the number. Treat any failing authentication record or blocklist entry as something to fix regardless of the overall score.
Related terms
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