Free tools
Free email authentication and DNS tools
Use these free tools to check the DNS records that email providers use to verify your messages. If you are setting up a sending domain, start with SPF, DKIM, and DMARC. If messages are being rejected or landing in spam, check PTR and MX records. Each tool explains what it checks and how to fix common problems.
12 tools FreeNo Prontuno account needed
Not sure where to start?
- Setting up a sending domain
- Check SPF first, then DKIM, then DMARC. DMARC only passes when SPF or DKIM passes for a domain that matches the From address.
- SPF — Free SPF checker DKIM — Free DKIM checker DMARC — Free DMARC checker
- Investigating one message
- Paste its raw headers into the email header analyzer to see its authentication results, sending IP, and the servers it passed through.
- Headers — Email header analyzer
- Mail isn’t arriving
- Confirm where the domain receives mail, then test whether those servers accept encrypted connections.
- MX — MX record checker TLS — SMTP TLS checker
3 tools
Email authentication
Check the records mailbox providers use to verify that mail really comes from your domain.
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SPF
Free SPF checker
Validate a domain’s SPF policy, inspect mechanisms, and count DNS lookups.
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DKIM
Free DKIM checker
Validate a DKIM public key by domain and selector, including algorithm, size, and revocation status.
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DMARC
Free DMARC checker
Review a domain’s DMARC policy, alignment, reporting addresses, and enforcement.
3 tools
Mail servers
Check where a domain receives mail and whether its mail servers are set up correctly.
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MX
MX record checker
Find the mail servers that receive email for a domain and compare their priorities.
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TLS
SMTP TLS checker
Test mail servers for STARTTLS or implicit TLS, certificate validity, and the negotiated TLS version.
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PTR
PTR and reverse DNS checker
Look up the reverse DNS (PTR) hostname for an IP address and confirm it resolves back to the same address.
3 tools
Domains and DNS
Look up a domain’s DNS records, the provider that hosts them, and who registered it.
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DNS
DNS record checker
Look up A, AAAA, CNAME, MX, TXT, NS, CAA, and SOA records.
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NS
Nameserver checker
Find a domain's authoritative nameservers and identify the DNS provider.
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RDAP
WHOIS and RDAP lookup
Look up domain registration data, registrar, status, nameservers, and DNSSEC via RDAP.
1 tool
Messages
Trace what happened to a specific email using the headers it arrived with.
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Headers
Email header analyzer
Inspect SPF, DKIM, and DMARC results, identify the sending IP, confirm reverse DNS, and trace the delivery path.
2 tools
Testing
Check a real message end to end, or test how your app handles bounces and deferrals.
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inspectemail.com
Inspect Email (opens in a new tab)
Send a message to a test mailbox and check its SPF, DKIM, and DMARC results and delivery details.
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mailboxsimulator.com
Mailbox Simulator (opens in a new tab)
Send to test addresses that deliver, defer, or bounce, and check how your app handles each outcome.
FAQ
Questions about these tools
- Which tool should I run first?
- For a new sending domain, check SPF and DKIM first, then set a DMARC policy. If you send from your own server or IP address, also check the PTR record.
- Are these tools free?
- Yes. Every tool on this page is free to use, and none of them needs a Prontuno account.
- Do the tools change my DNS records?
- No. They only read public DNS records. You make any changes at your DNS provider.
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