Email deliverability test

What does an email deliverability test check?

Five things: whether the domain can receive mail, which servers may send as it, whether its messages are signed, what receivers should do when those checks fail, and whether receivers are refusing it outright.

MX — can the domain receive mail at all

No MX record means no address at the domain can receive anything. In practice a missing MX is usually a typo in the domain rather than a domain with no mail.

SPF — which servers may send as you

A DNS record listing authorised senders. The common faults are having none, having two (which is invalid and fails outright), and quietly exceeding the ten-DNS-lookup limit, which breaks the whole record rather than part of it.

DKIM — a signature proving the message was not altered

Keys live at selector-specific hostnames that cannot be enumerated from DNS, so this test probes the selectors the major providers use. A negative result means inconclusive, not absent — a custom selector will not be found.

DMARC — what receivers should do when the above fail

The policy is the entire point. p=none turns reporting on and blocks nothing, so a domain sitting on it is compliant with the 2024 Google and Yahoo requirement and still fully spoofable.

Blocklists — whether receivers are refusing you outright

A listing on a major list explains a sudden, total collapse in delivery better than anything else. Note that a check reported as unavailable means the list refused our query, not that you passed — we would rather say so than imply a result nobody verified.

Why does my email still bounce when every check passes?

Because authentication and bounces are separate problems, and they get conflated constantly. Authentication records prove you are allowed to send as your domain. They say nothing whatsoever about whether the addresses you are sending to still exist.

A domain can score 100% here and still get throttled, because lists decay as people change jobs and a high bounce rate is one of the signals mailbox providers use to limit a sender. Fix the records, then fix the list, in that order: the records take minutes, and the reputation damage from a bad send takes far longer to undo.

How do I test email deliverability to Gmail and Outlook?

Start with this test, because both providers check the same records before anything else. Google’s email sender guidelines require SPF or DKIM for every sender, and SPF, DKIM and DMARC for bulk senders. Outlook.com has similar rules for high-volume senders; the Microsoft sender requirements checker tests a domain against them.

Records only tell you whether you are allowed in. To see where a real message lands, send one to a Gmail and an Outlook account you control, check the inbox and spam folders, and paste the headers into the email header analyzer to see what each check returned for that message. For Gmail reputation over time, use Google Postmaster Tools.

How do I test my email deliverability?

1. 1Enter your sending domain, the part after the @ in your From address.
2. 2Run the test. It looks up MX, SPF, DKIM (at the selectors the major providers use), DMARC, and the domain's status on major blocklists.
3. 3Read each line: pass, fail or unavailable, with what was found. Each label links to a plain explanation.
4. 4Fix what failed with the SPF generator or DMARC generator, wait for DNS to update, then run the test again.

Example

You enter

The sending domain acme.example.

You get

4 of 5 checks passed: MX found (primary aspmx.l.google.com), SPF present with soft fail (~all), but no DMARC record, so spoofing the domain is unrestricted. A check the tool couldn't run shows as unavailable, never as a pass.

Limits

Ten audits a minute per IP address, one domain at a time; DNS lookups only, nothing is sent to the domain.

Is a DNS audit the same as an inbox placement test?

No. This test reads your DNS records. A seed or inbox placement test sends real messages to test accounts and reports where they landed. They answer different questions:

Fix the records first, since a seed test on a domain with a broken record mostly measures the broken record.

Who uses this tool, and for what?

Cold emailers

Check every new outreach domain before warming it up, so you do not spend weeks building reputation on a domain whose SPF record already fails.

Agencies

Run a prospect's domain on a sales call and show them, line by line, which record is missing. Then fix it with the SPF checker and DMARC checker.

IT admins

After moving mail to a new provider, confirm that MX, SPF and DKIM point at the new service and that DMARC is still published.

Marketers

Before a big send, confirm the domain meets the authentication part of the Google and Yahoo bulk sender rules. The bulk sender checker covers the rest of the list.

What can’t this tool tell you?

• DKIM keys live at selector names that cannot be listed from DNS. The test tries the selectors major providers use, so a custom selector shows as not found even when DKIM works.
• Blocklist coverage is the major lists only. A list reported as unavailable refused our query; it is not a pass.
• It reads DNS, so it cannot see your sending reputation, complaint rate, content or where a message lands. Use Google Postmaster Tools for Gmail reputation.
• It checks that records exist, not that a given message aligned with them. To see what a real message passed, paste its headers into the email header analyzer.
• DNS changes can take time to show up because of caching, so a record you just fixed may still fail for a while.

Sources

• RFC 7208: Sender Policy Framework (SPF)
• RFC 6376: DomainKeys Identified Mail (DKIM)
• RFC 7489: DMARC
• Google: Email sender guidelines

Common questions

How do I test my email deliverability?

Start with the records that decide whether receivers trust you: MX, SPF, DKIM and DMARC, plus whether your domain appears on a major blocklist. Enter a domain above and all five are checked in a few seconds. Every check is a DNS lookup, so nothing is sent to the domain and the test is invisible to it.

Why is my email going to spam?

In rough order of frequency: missing or misaligned authentication, a poor sending reputation from bounces and complaints, a blocklist listing, and low recipient engagement. This tool settles the first and third in seconds. Reputation and engagement are earned over weeks of sending behaviour and cannot be checked from DNS.

What is a good email deliverability score?

Treat anything below 100% as work to do, because each of these checks is pass or fail rather than a spectrum. The one people most often skip is DMARC: publishing p=none satisfies Google and Yahoo's bulk sender requirement while enforcing nothing at all, so a domain can look compliant and still be freely spoofable.

How do I test email deliverability for free?

Run this test on your sending domain, then send a message to a Gmail and an Outlook account you own and see which folder it lands in. Both are free; the first finds broken records, the second shows placement for those two inboxes.

Does this test show whether my email lands in spam or Promotions?

No. It reads DNS records and never sends a message, so it cannot see folder placement. Placement depends on the records it checks plus reputation, content and engagement, which only a real send reveals.

Does this test send an email to my domain?

No. Every check is a DNS query — MX, TXT and blocklist lookups. Nothing is transmitted to your mail server, nothing arrives in anyone's inbox, and the domain owner sees no trace of the test.

My records all pass but email still bounces. Why?

Authentication and bounces are unrelated problems. These records prove you are allowed to send as your domain; they say nothing about whether the addresses you are sending to exist. A hard bounce means that specific mailbox is gone, and the only fix is removing it before the send rather than discovering it afterwards.

Fix a failing record

Build a valid SPF record or DMARC record, or check one at a time with the SPF, DKIM and DMARC checkers.