Email Deliverability Tools
Instant checks with plain-English verdicts and the exact fix for every failure. Free, no login, no limits.
Free email deliverability tools, built by consultants
Every tool on this page exists because we use it in real client work. Postbox Consultancy Services has spent 10+ years fixing email deliverability for 500+ clients - blacklist recovery, authentication rollouts, cold email infrastructure - and these are the checks we run first on every engagement. Each result comes with a plain-English verdict and, when something fails, the exact DNS record to paste.
Domain Health report
One input runs SPF, DKIM, DMARC, MX, BIMI, MTA-STS, TLS-RPT and DNSSEC checks in parallel and grades your domain A to F. The fastest way to see whether your email authentication meets the Gmail and Yahoo bulk sender requirements.
SPF record checker
Validates your SPF record syntax and recursively counts DNS lookups against the RFC 7208 limit of 10 - the invisible cause of SPF PermError failures. Flags +all misconfigurations, missing all mechanisms, void lookups and the deprecated ptr mechanism.
DKIM record lookup
Checks any selector, or probes 15 common selectors automatically if you do not know yours. Grades RSA key strength (1024 vs 2048-bit), detects revoked keys and Ed25519 signatures.
DMARC checker
Parses every DMARC tag - policy, subdomain policy, reporting addresses, alignment modes and percentage - and tells you the exact next step on the path from p=none to p=reject.
BIMI lookup
Checks your BIMI record, previews the published SVG logo and verifies whether a VMC certificate is referenced - the requirements for showing your brand logo in Gmail, Yahoo and Apple Mail.
MX record lookup
Lists mail servers by priority with resolved IP addresses and identifies your mail provider - Google Workspace, Microsoft 365, Zoho and others.
Reverse DNS / PTR check
Looks up the PTR record for any IPv4 or IPv6 address and verifies forward-confirmed reverse DNS (FCrDNS) - the check Gmail and Microsoft run against every sending IP.
Email header analyzer
Paste raw headers to see SPF, DKIM and DMARC verdicts as evaluated by the receiving server, plus a hop-by-hop delivery timeline that highlights where mail was delayed.
MTA-STS and TLS-RPT check
Verifies the DNS records behind inbound TLS enforcement and TLS failure reporting - increasingly expected for business domains handling sensitive mail.
DNS lookups
A, AAAA, TXT, CNAME, NS, SOA and CAA record lookups for everyday DNS diagnostics, with TTLs shown for every record.
Frequently asked questions
Are these email deliverability tools really free?
Yes. Every tool on this page is free with no login, no lookup limits and no paywalled results. They are built and maintained by Postbox Consultancy Services, an email deliverability consultancy.
What is the SPF 10 DNS lookup limit?
RFC 7208 allows an SPF record to trigger at most 10 DNS lookups, counting every include, a, mx, ptr, exists and redirect mechanism recursively. Exceeding 10 causes a PermError, which means SPF silently fails at most mail receivers. Our SPF checker counts the lookups recursively and shows exactly which mechanisms consume them.
What does DMARC p=none mean?
p=none is DMARC monitoring mode: receivers report authentication failures to you but still deliver spoofed mail normally. It is the correct starting point while collecting reports, but domains should progress to p=quarantine and then p=reject for real protection.
How do I find my DKIM selector?
Open any email you have sent and view its raw headers: the DKIM-Signature header contains s=, which is your selector. Or leave the selector blank in our DKIM lookup and it probes 15 common selectors automatically.
Why does reverse DNS (PTR) matter for email deliverability?
Gmail, Microsoft and most receivers check that a sending IP has a PTR record and that the PTR hostname resolves back to the same IP (forward-confirmed reverse DNS). Sending IPs without valid rDNS are rejected or heavily penalized. Test yours with the reverse DNS check.
Do you store the domains I look up?
No. Your lookups are never stored or shared by Postbox Consultancy Services.
Did one of your checks fail?
Postbox Consultancy Services has fixed deliverability for 500+ clients over 10+ years - blacklist recovery, authentication setup, cold email infrastructure and full audits.