{"server":{"name":"warminboxes-deliverability-tools","title":"WarmInboxes Free Deliverability Tools","version":"1.0.0"},"transport":"streamable-http","protocolVersions":["2025-06-18","2025-03-26","2024-11-05"],"endpoint":"https://warminboxes.com/mcp","tools":[{"name":"check_deliverability","description":"Grade a domain A-F for cold email readiness. Checks SPF, DKIM, DMARC, MX, blacklists and domain age together and returns a weighted score with a per-check breakdown and what to fix. Start here for open-ended \"is this domain any good\" questions."},{"name":"check_spf","description":"Look up a domain's SPF record and validate it, including the recursive DNS lookup count that silently breaks SPF past 10."},{"name":"check_dkim","description":"Find and validate a domain's DKIM signing key, including key strength. Leave selector empty to auto-scan 26 common selectors (google, selector1, k1, and the rest). When no key is found, reports whether the selectors are delegated by CNAME to a provider that has not published one — the usual Microsoft 365 failure, where the records are right but signing was never switched on."},{"name":"check_dmarc","description":"Look up and parse a domain's DMARC record: policy, subdomain policy, percentage, alignment and reporting tags, each explained."},{"name":"check_bimi","description":"Validate a domain's BIMI record, the logo SVG, the VMC, and the DMARC enforcement level Gmail requires before it will show a brand logo."},{"name":"check_mta_sts","description":"Validate a domain's _mta-sts DNS record and its published policy file: mode, MX patterns, max_age and TLS-RPT."},{"name":"check_ssl","description":"Read a host's TLS certificate: issuer, validity dates and days remaining, subject alternative names, key type and size, signature algorithm, chain, negotiated protocol and whether the chain is trusted and covers the hostname. Use it on an MTA-STS policy host (mta-sts.<domain>) or a click-tracking domain, where an expired certificate stops mail or turns every click into a browser warning. Port 25 is not reachable from serverless, so the certificate an MX host presents cannot be read this way."},{"name":"check_dns","description":"Query any DNS record type for a domain: MX, TXT, A, AAAA, CNAME, NS, SOA, CAA."},{"name":"lookup_txt","description":"Every TXT record on a domain, with each one identified (SPF, DKIM, DMARC, MTA-STS, TLS-RPT, BIMI, or which service's ownership token it is), plus the four underscore names a receiver reads — _dmarc, _mta-sts, _smtp._tls and default._bimi — in the same lookup. Names the three mistakes that are invisible from reading the records: more than one SPF record, which makes a receiver return permerror so SPF fails entirely; a DMARC or DKIM record published at the apex, where nothing will ever read it; and a record longer than one 255-byte TXT string. Use this before concluding a record is missing, because the usual cause of a missing DMARC record is a DMARC record at the wrong name."},{"name":"check_rdns","description":"The PTR record for an IPv4 or IPv6 address, and the forward lookup that decides whether it counts. Reverse DNS is delegated to whoever holds the address block, so a PTR alone proves nothing — the operator of an IP can point it at any hostname, including one they do not own. Only the round trip is evidence: PTR names a host, that host resolves back to the same address. That pair is forward-confirmed reverse DNS (FCrDNS), it is what Google and Yahoo mean when they list forward and reverse DNS among their bulk sender requirements, and it is what `fcrdns` reports. Over IPv6 it is stricter still: Gmail rejects IPv6 mail from an address without it, where the same mail over IPv4 would be accepted. Reports a missing PTR separately from a PTR that fails to confirm, because the fixes differ and only the address block's operator — usually the hosting provider, not the sender — can set either."},{"name":"check_blacklist","description":"Check a domain or IP against 20+ major email blacklists (Spamhaus, Barracuda, SORBS and others) and report which list it appears on."},{"name":"check_surbl","description":"Check domains against the SURBL URI blacklist in bulk. URI blacklists list the domains that appear inside a message body, so a listed tracking or landing domain sends the whole email to spam however clean the sender is. Up to 100 domains per call."},{"name":"check_nameservers","description":"Get the NS records and the DNS provider behind one domain or a whole list. Useful for working out who actually controls a domain's DNS before trying to fix its records."},{"name":"check_domain_expiry","description":"Get a domain's registrar, creation date, expiry date and days remaining, over RDAP with a WHOIS fallback for ccTLDs that publish no RDAP service. Domain age is one of the strongest cold-email risk signals."},{"name":"check_google_domain","description":"Tell whether a domain is already attached to a Google Workspace account, or is clear for a fresh Google tenant."},{"name":"check_cname","description":"Follow a host's full CNAME chain and flag the mistakes that break a cold-email tracking domain. Pass expected to assert where the chain should end up."},{"name":"verify_email","description":"Check email addresses for syntax, live MX records, disposable providers and role prefixes (info@, sales@). Does not open SMTP connections, so catch-all domains come back valid."},{"name":"lookup_mx","description":"Look up a domain's MX records with priorities and resolved IPs, and identify the mailbox provider (Google Workspace, Microsoft 365, Zoho, Fastmail and others) and any security gateway in front of it (Mimecast, Proofpoint, Barracuda and others). Pass `domains` instead of `domain` for up to 100 at once, which also returns a provider breakdown. Reports a null MX (RFC 7505) rather than treating it as a broken record, and does not guess the provider behind a gateway, because that is not observable from the MX."},{"name":"segment_esp","description":"Split a list of domains by the email provider behind them (Google, Microsoft, or a security gateway) from their MX records. Sending Google-to-Google and Microsoft-to-Microsoft is one of the larger levers on inbox placement."},{"name":"plan_infrastructure","description":"Work out how many inboxes and domains a daily cold email volume needs, and what it costs per month. Use this for \"how many inboxes do I need for N a day\". Give dealValue to get the revenue and ROI math as well."},{"name":"expand_spintax","description":"Expand a spintax template such as \"{Hi|Hey} there\" and render its Liquid merge tags, returning the total number of variations, every variable the template references, any variable with no value and no default, and a set of rendered samples. Use it to check a sequence before it sends."},{"name":"generate_unsubscribe","description":"Build a CAN-SPAM and GDPR compliant opt-out footer in plain text and HTML, with a checklist saying which compliance requirements the details given actually satisfy. A footer with no postal address is the usual failure."}],"usage":"POST JSON-RPC 2.0 to this URL. No authentication. Add it to any MCP client as a Streamable HTTP server.","docs":"https://warminboxes.com/llms.txt"}