MTA-STS Checker

Other free deliverability tools

The rest of the toolkit, all free and all without an account.

• Blacklist Checker — Check if your domain or IP is listed on 20+ major email blacklists in seconds.
• Domain Reputation Checker — Work out whether your domain is actually the problem — what’s listed, what’s broken, and what it rules out.
• Deliverability Checker — Grade your domain A to F across SPF, DKIM, DMARC, MX, blacklists and domain age.
• DMARC Report Analyzer — Read the daily DMARC XML your domain receives: who sends as you, what passed, what only failed alignment.
• DMARC Checker — Validate and analyse your DMARC record, policy, tags and verdicts explained.
• SPF Checker & Generator — Look up existing SPF records or build a new one, with recursive lookup counting.
• DKIM Checker — Auto-scan 26 common selectors and validate your DKIM signing key strength.
• MX Lookup — Look up a domain’s MX records with priority, address and TTL, and identify the mail provider behind them.
• Email Provider Checker — Find out who hosts a domain’s email — Google, Microsoft, Zoho, or a security gateway — from one lookup.
• Bulk MX Lookup — Look up the mail provider behind a whole list of domains at once, with the split and a CSV to segment from.
• SPF Lookup Counter — Count the DNS lookups your SPF record costs, see the include tree, and find out how close you are to the limit.
• DKIM Selector Finder — Find which DKIM selectors a domain publishes without knowing the selector first. Scans 26 common ones.
• Email Authentication Checker — SPF, DKIM, DMARC, MX, BIMI and MTA-STS for one domain in one pass, with the optional ones marked optional.
• DMARC Alignment Checker — Paste a real message’s headers and find out why DMARC failed when SPF or DKIM passed.
• One-Click Unsubscribe Checker — Check whether a message’s List-Unsubscribe headers meet the one-click requirement Google and Yahoo enforce.
• Reverse DNS Lookup — Look up the PTR record for an IP and check whether it forward-confirms, which is the pair receivers test.
• IP Reputation Checker — Blocklist listings and reverse DNS for a sending IP, reported as findings rather than an invented score.
• Tracking Domain Checker — Check the domain your tracked links point at: DNS, certificate, URL blocklists, and whether it is yours or your platform’s.
• Gmail Clipping Checker — Find out whether Gmail will clip your email at 102KB, and exactly what is taking up the room.
• Email Link & Pixel Scanner — Pull every link, image host and tracking pixel out of an email and check each domain against URL blocklists.
• Bulk Sender Requirements Checker — Check the Gmail, Yahoo and Microsoft bulk sender requirements — and see which ones no external tool can verify.
• DNS Checker — Query MX, TXT, CNAME, A and all other DNS record types for any domain.
• TXT Record Lookup — Every TXT record on a domain, each one identified — plus the mistakes that quietly break authentication.
• A Record Lookup — The IPv4 addresses a hostname resolves to, with TTLs, the CNAME chain, and whether they are public at all.
• AAAA Record Lookup — The IPv6 addresses a hostname resolves to, and why an unwanted AAAA record on a mail host costs you delivery.
• SOA Record Lookup — The zone’s SOA record, read for the field that decides how long a new DNS record keeps reading as missing.
• Domain Expiry Checker — Monitor domain expiration dates and catch renewals before they lapse.
• Record Generator — Build correct SPF, DKIM and DMARC records with presets for every major ESP.
• ESP Segmentation & Mailbox Calculator — Split your list by Google, Microsoft and gateway inboxes, then get told how many mailboxes to buy.
• Cold Email Infrastructure Calculator by Recipient ESP — Upload your list and get the exact Google, Microsoft and Azure inboxes to buy for the people on it.
• Nameserver Checker — One domain or a whole CSV: get NS records and the DNS provider behind every domain.
• SURBL Checker — Bulk-check domains against the SURBL URI blacklist.
• Spamhaus DBL Checker — Bulk Spamhaus Domain Block List lookups for your sending and link domains. Coming soon.
• Google Domain Checker — See if a domain is already tied to a Google Workspace account or clear for fresh inboxes.
• Email Verifier — SMTP-level mailbox verification with catch-all detection.
• Spam Checker — Scan your subject and body for 200+ weighted spam triggers and formatting red flags.
• CSV List Cleaner — Dedupe and scrub lead lists entirely in your browser, nothing gets uploaded.
• Spintax & Liquid Tester — Preview every spintax variation and personalization variable before sending.
• Domain & Inbox Planner — Target volume in, exact domains and inboxes needed out, with a safe ramp-up plan.
• Inbox Rotation Planner — Split your fleet into rotating batches with a schedule, no burned inboxes.
• Pre-Send Checker — Catch broken merge tags, dupes and spintax errors, and forecast send volume.
• Suppression Checker — Check any list against customers, unsubscribes and previously contacted companies.
• Bounce Analyzer — Paste bounce messages, get the root cause in plain English plus a pause-or-continue verdict.
• Outlook SCL Analyzer — Paste Outlook headers and find out exactly why the message went to Junk.
• Waterfall Calculator — Find the cheapest verifier order and your true cost per usable email.
• Sequencer CSV Converter — Convert lead CSVs between Instantly, Smartlead and Email Bison formats.
• CSV Combiner — Merge multiple lead lists into one, matching headers and deduping emails.
• Unsubscribe Generator — CAN-SPAM and GDPR compliant opt-out footers in plain text and HTML.
• Inbox Previewer — See your sender, subject and snippet exactly as Gmail and Outlook render them.
• Header Analyzer — Paste raw headers: SPF, DKIM, DMARC, alignment and hops explained in plain English.
• BIMI Checker — Validate your brand logo record, SVG, VMC and the DMARC enforcement Gmail requires.
• CNAME Checker — Follow the full CNAME chain and catch the mistakes that break a cold email tracking domain.
• SSL Certificate Checker & Generator — Read any host’s TLS certificate — issuer, expiry, names and chain — or build the config for a new one.