Email deliverability test
Send a real email to our test address and get a deliverability report back by email: authentication, sending server, blocklists, content and the Gmail, Yahoo and Microsoft sender rules.
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Send any email to
- Send from the mailbox or email service you want to test. A real message works best.
- Put the address in To or Cc, not Bcc.
- The report comes back to your From address, usually within a minute.
Replies go only to messages signed with DKIM by the From domain, so nobody can use this address to email someone else. SPF may fail.
No reply after a few minutes?
- Look in spam or junk for a message from email-test@zerobounce.ai with a subject starting “Email test:”.
- Check that the message was signed with DKIM by your From domain. The DKIM checker shows what your domain publishes; without a valid signature there is no reply, by design.
- Check that our address was in To or Cc, not Bcc, and that the From address can receive mail.
- Each address gets 2 tests a day, and each company domain 3. Past that there is no reply until the next day (UTC). Rarely, the test’s own daily sending quota runs out for everyone.
- Bounces, auto-replies, messages over 10 MB and mail from zerobounce.ai’s own addresses never get a reply.
There is no status page or resend button: the test only answers by email. Once you’ve fixed the cause, send a new message. Messages turned away for a missing signature or Bcc don’t use up a test. To check a message without sending it, paste the whole message into the spam score tool.
This is a limited free test: 2 tests per sender address a day, and 3 per company domain. For professional deliverability testing (inbox placement across 20+ mailbox providers, blacklist monitoring and more), use ZeroBounce’s Inbox Placement Test.
How the email deliverability test works
The email test grades one real message the way a receiving mail server would. You send it to email-test@zerobounce.ai from the system you want to check, and the report comes back by email. It suits anyone setting up a new domain, email service or mail server.
What happens to your message
The message arrives through Cloudflare Email Routing. The test reads the sending IP address, HELO name and TLS status from the top Received block, the one added by the server that received it, and ignores the lines below, which the sender wrote.
It then evaluates SPF for that IP and the envelope sender (RFC 7208), verifies up to five DKIM signatures against their published keys, and looks up DMARC for the From domain. The content goes through the same rules as the spam score tool, fed with the test’s own authentication results. Blocklist rows count the lists that answered and say how many couldn’t be checked, so a list that didn’t answer is never counted as clean.
How to read the report
The report opens with a grade, A+ to F, worked out like the spam score but with extra points for what only a real delivery shows: reverse DNS, TLS, blocklist listings, Spamhaus reputation, DKIM key details and a DMARC policy of p=none. Under it, Fix first lists up to 12 problems, failures before warnings and the costliest first.
What the extra findings mean
- An RSA DKIM key under 2048 bits. Rotate to a 2048-bit key.
- A DKIM signature whose
l=covers only part of the body. Anything appended later still verifies. Sign withoutl=. - DMARC at
p=none. Spoofed mail using your domain is still delivered; move to quarantine or reject once reports look clean. - No reverse DNS on the sending IP, or a PTR name that doesn’t resolve back. Ask whoever runs the IP for a matching PTR record, then confirm it with the reverse DNS check.
- Sent without TLS. The message reached the test over an unencrypted connection. Turn on STARTTLS in the sending server or app.
When to run it
Run it after you change DNS records, switch email services or move to a new sending IP, and again before a large send. One test shows how one message was received on one day; it doesn’t predict where every mailbox provider will file your mail.
Updated · Maintained by Liviu Tanase
Questions
How do I test if my emails go to spam?
Send a real message to email-test@zerobounce.ai from the system you send with. The report judges it the way a receiving server would: SPF, DKIM and DMARC, reverse DNS and TLS, the sending IP and the message’s domains on blocklists, and the same content rules as the spam score tool, then grades it A+ to F. It can’t tell which folder one particular mailbox provider will choose: that takes test mailboxes at each provider (an inbox placement test).
Can I test a newsletter from my email marketing service?
Yes. Add email-test@zerobounce.ai as a test recipient in To or Cc (Bcc gets no reply) and send the real campaign. The checklist covers the Gmail, Yahoo and Microsoft bulk-sender rules, including one-click unsubscribe. The report goes to the From address, and only when the service signs the message with DKIM for that domain, a parent or a subdomain of it, so set up your DKIM records first.
What does the report check?
SPF for the server that sent the message, up to five DKIM signatures (verified, with key size), DMARC policy and alignment, forward-confirmed reverse DNS of the sending IP, whether the message arrived over TLS, the sending IP and the message’s domains (From, envelope sender, DKIM signer and the domains it links to, up to six in all) on public and keyed blocklists including Spamhaus and Abusix, Spamhaus Intelligence for the sending IP’s listing history and the domain’s reputation score, a spam check of about 50 content and header rules with the points for each, and a checklist of the Gmail, Yahoo and Microsoft bulk-sender rules.
Why didn’t I get a reply?
Replies go only to senders that prove who they are: the message needs a DKIM signature that verifies, signed by the From domain (or its parent or a subdomain of it), and our address must be in a signed To or Cc header, so not in Bcc. SPF may fail. There is also no reply past the daily limits (2 tests per sender address, and 3 per domain for company domains; big free mail domains such as gmail.com have no domain limit), and none to bounces, auto-replies, messages over 10 MB or zerobounce.ai’s own addresses. If DKIM is the problem, the DKIM checker shows what is published for your domain.
Why does it need DKIM?
So the address can’t be used to send mail to someone who never wrote to it. A From address is easy to fake; a DKIM signature from the From domain isn’t. Without that check, anyone could make zerobounce.ai email a report to any address they typed in a From header.
Is my message stored?
The message is read in memory to build the report and is not stored by zerobounce.ai. Cloudflare, which receives your message and sends the report, logs the sender and recipient addresses, subject line, time and delivery result of both, and may keep short-lived copies of the messages it sends. To enforce the daily limits, a hash of the sender address and domain is kept for two days, and daily counts of outcomes for eight. The sending server and the domains in your message are also checked against public blocklists.
What should I send?
The message you actually want to test: send it from the mailbox, server or email service your real mail goes out through, with your real content. Most services let you add a test recipient or send a test to a seed address. The report goes back to the From address, so use one that can receive mail.
Why is it limited?
It is a free, quick check: 2 tests per sender address a day, and 3 per domain a day for company domains. Big free mail domains such as gmail.com and outlook.com have no domain limit, only the per-address one. For professional deliverability testing, such as inbox placement across 20+ mailbox providers, blacklist monitoring and more, use ZeroBounce’s Inbox Placement Test.
How is this different from the spam score tool?
The spam score tool scores a message you paste, so it can only read the authentication results your mailbox wrote. This test receives the message itself, so it verifies DKIM, evaluates SPF and DMARC, checks the sending server and its reputation as a receiving mail server would, and then applies the same content rules.