Free email tools
Diagnostics for the parts of email that break quietly. Each one tells you what it found and how to read it.
Two things separate these from the usual set. Every page carries a section on reading the result and what to check next, because a checker that only reports good news teaches you the wrong lesson about your own mail. And when a lookup fails, you get the error rather than a plausible-looking result.
Authentication
The DNS records that decide whether receivers believe you are who the From: line says.
SPF checker
Reads the record, follows every include, and counts the DNS lookups against the limit of ten that most broken records have quietly crossed.
DMARC checker
Reads the policy at _dmarc and tells you what receivers are being asked to do, how much mail it covers, and whether anyone is collecting reports.
DKIM checker
Looks up a public key by selector, or tries the selectors the large platforms use. Flags revoked keys and keys left in test mode.
SPF generator
Builds a record from the platforms that send your mail, with a running lookup count so you see the ceiling before you publish.
DMARC generator
Builds a policy record and warns about the settings that break working mail, starting with strict alignment.
Diagnosis
For when a message went somewhere unexpected and you need to know where.
Email header analyzer
Paste raw headers for the full path, the delay at every hop, and the SPF, DKIM and DMARC results the receiving server recorded. Runs in your browser.
MX lookup
Mail exchangers in priority order, each resolved to an address, which is how an exchanger that no longer resolves shows itself.
Blacklist checker
Checks an IP or domain against the public blocklists receivers actually query, with each list's own reason text.
Lists and copy
The numbers that decide whether your next campaign reaches anyone, and the text that gets read.
Bounce rate calculator
Your rate against the thresholds providers respond to: under 2% healthy, over 5% at risk, and what the middle band is telling you.
Complaint rate calculator
Your rate against Google's published targets for bulk senders, plus why your ESP's figure is lower than the one Google acts on.
Spam word checker
Flags trigger phrases and the formatting patterns filters weigh more heavily. Returns findings, not a score nobody can justify.
Disposable email checker
Matches a domain against a bundled list of throwaway providers, and is clear that a list-based check is always behind.
Email syntax checker
Checks an address against the RFC shape rules, and explains why passing proves nothing about whether the mailbox exists.
Which tool answers which question
| The question | The tool | Where it runs |
|---|---|---|
| Why did this message go to spam? | Header analyzer | Your browser |
| Is my authentication set up correctly? | SPF, DKIM and DMARC checkers | Our resolver |
| Can this domain receive mail at all? | MX lookup | Our resolver |
| Is my sending IP blocked somewhere? | Blacklist checker | Our resolver |
| Is my list healthy? | Bounce and complaint calculators | Your browser |
Addresses, servers and test sends
Tools that talk to a real mail server or read a real message you send. Nothing is ever sent to the address you check.
Bounce checker
Asks the mail server about one address at RCPT TO and closes before DATA, so you know if a send would hard-bounce.
Is this email real?
Confirms whether a mailbox exists, and flags throwaway domains, role inboxes and typos like gmial.com.
Fake email checker
Catches invented mailboxes, dead domains and burner inboxes before they reach your sign-up list.
Catch-all checker
Probes a random mailbox at the domain to show whether its server says yes to every address.
SMTP test
Opens a session on port 25 from our servers and shows the banner, EHLO extensions and response time.
Email TLS checker
Asks the mail server for STARTTLS and reports the TLS version and cipher it negotiates.
Email deliverability test
Send one email to a test address and get a score out of 10, with SPF, DKIM, DMARC and blocklist results.
Email spam checker
Send your draft to a test address and see every phrase, link and setting that counts against it.
List work and key setup
Browser-only tools for pricing, cleaning and grading a list, reading DMARC reports and making DKIM keys. Nothing you paste or open is uploaded.
Email verification cost calculator
Your ZapBounce price for any list size, with duplicates and unknowns taken out, beside the published packs of five other verifiers.
DMARC report analyzer
Open the .zip, .gz or .xml reports receivers send and see your pass rate and every IP sending as your domain.
DKIM record generator
A 2048-bit key pair made by WebCrypto in your browser, plus the TXT record to publish.
Email extractor
Every address in a page, thread or CSV, lowercased and deduplicated, ready to download.
Remove duplicate emails
Cleans repeats out of a list, with case and plus-tag folding, and shows what repeated.
Email list quality score
A grade from A to F for a sample of your list, on a rubric printed in full.
List decay calculator
How much of your list has gone stale since the last check, at Hunter's measured 5.5% every eight weeks.
Role account checker
Finds info@, sales@ and the other role inboxes ZapBounce flags, and hands back the list without them.
Domain setup and reputation
Live DNS checks for the records and lists around a sending domain, from one-shot health checks to single records.
Domain health check
Nine checks at once, MX to BIMI, scored on a rubric printed in full on the page.
Domain reputation checker
The domain on domain blocklists and the IPs of its web and mail servers on IP blocklists, in one pass.
Email domain checker
Confirms a domain exists and can receive mail, and flags disposable, free and misspelled domains.
Email provider lookup
Names the mailbox host, any security gateway in front of it, and the services in its SPF record.
MTA-STS checker
Reads the record, fetches the policy file over HTTPS and matches it against every live MX host.
BIMI record checker
Tests the logo and certificate links and confirms DMARC is strict enough for a logo to show.
Reverse DNS lookup
The PTR record for any IPv4 or IPv6 address, forward-confirmed back to the same IP.
Every tool
All of them, alphabetically. Each page explains how to read its result.
Questions people ask
Do I need an account?
No. There is no sign-up, no key and no limit worth mentioning on any of these pages.
Is what I paste into the header analyzer uploaded?
No. It is parsed in your tab and never leaves the browser. That matters here because a header block carries the recipient's address and the hostnames of their internal mail estate.
Why does a DNS tool sometimes say it has no result?
Because the lookup did not happen. A resolver timed out or our service was unavailable, and showing you a record we did not fetch would be worse than showing you nothing.
Which tool should I start with?
If something already went wrong, the header analyzer, because the answer is usually in the message itself. If you are setting up a domain, the SPF checker followed by the DMARC checker.
Every one of these reads a record. None of them reads a mailbox.
Verification is the other half: an SMTP conversation about a specific address, with a verdict for each address and no charge for an unknown.