Free Email Deliverability Tools

Free Email Deliverability Tools: Diagnose, Validate, and Fix

Email deliverability problems are almost always diagnosable before you send — if you know where to look. These free browser-based tools cover every major diagnostic area: authentication record validation, DNS blacklist checking, IP reputation analysis, domain reputation monitoring, and list hygiene assessment. All tools run directly from your browser using DNS-over-HTTPS. No sign-up. No data sent to our servers.

Authentication Tools: SPF, DKIM, and DMARC

The three pillars of email authentication — SPF, DKIM, and DMARC — are now mandatory for high-volume senders. Gmail and Yahoo reject unauthenticated bulk mail. Microsoft uses authentication signals to determine Junk folder placement. Our authentication checkers verify live DNS records for any domain in seconds.

The SPF Validator retrieves and parses SPF records, counts DNS lookups (critical — the 10-lookup limit is a common source of authentication failures), detects authorized sending services, and validates the ending mechanism. The DKIM Checker validates public key records for any domain and selector, confirming the key is present and not revoked. The DMARC Checker retrieves and analyzes DMARC policy, checking enforcement level, aggregate reporting configuration, and alignment settings.

Blacklist Tools: IP and Domain Reputation

The IP Blacklist Checker checks a single IP against 34 DNSBLs grouped by impact tier, with a weighted reputation gauge, donut chart breakdown, ISP impact analysis, and recommendations. The Domain Blacklist Checker checks a domain against 18 URI blacklists including all SURBL components and URIBL. Both include direct delisting links for any active listings.

For auditing multiple addresses at once, the Bulk IP Blacklist Checker handles up to 100 IPs with CSV export, and the Bulk Domain Blacklist Checker handles up to 100 domains.

DNS Lookup Tools

The MX Lookup retrieves MX records for any domain and identifies the mail provider. The PTR Lookup checks reverse DNS records and verifies forward-confirmed rDNS (FCrDNS) — a proper PTR record is required for deliverability to most ISPs. The TXT Record Lookup retrieves all TXT records for any domain or subdomain, automatically identifying SPF, DKIM, DMARC, and BIMI records. The BIMI Checker verifies BIMI configuration including logo URL and VMC.

Record Generators: Build Valid DNS Records

The DKIM Key Generator creates RSA 2048, RSA 4096, or Ed25519 key pairs directly in your browser using the Web Crypto API — no server involved, keys are generated locally. The SPF Record Builder lets you select sending services from a checklist and builds a valid SPF record while tracking the 10-lookup limit in real time. The DMARC Generator produces a valid DMARC TXT record with configurable policy, reporting address, and alignment settings.

Deliverability Calculators and Analyzers

The Bounce Rate Calculator computes hard bounce, soft bounce, and spam complaint rates against ISP thresholds — flagging when rates approach or exceed the levels that trigger filtering or sending blocks. The List Hygiene Calculator estimates your deliverable list size based on engagement segments. The Subject Line Spam Trigger Tester analyzes subject lines for spam keywords, excessive caps, and other patterns that increase filtering risk. The Email Address Validator validates syntax and optionally checks domain MX records in bulk.

Diagnosing Problems vs. Fixing Them

These tools excel at diagnosing deliverability problems. Diagnosing is the first step. The second step — actually fixing the structural issues — usually requires infrastructure changes: dedicated IP pools with proper warming, actively monitored sending reputation, separated transactional and promotional streams, and clean list acquisition practices.

If you're checking multiple tools and finding problems across authentication, blacklisting, and bounce rates simultaneously, you're likely looking at an infrastructure problem rather than a content or list problem. Our team can provide a free infrastructure assessment and identify the structural root cause.