Free email tools
Diagnostics for the parts of email that break quietly. Each one tells you what it found and, just as plainly, what it could not settle.
Two things separate these from the usual set. Every page carries a section naming what the tool cannot tell you, 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 |
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 the ones nobody can settle labeled rather than guessed.