WarmInboxes Free Deliverability Tools

What you can do with it

We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.

• Connection: Runs in the cloud
• Transport: Streamable HTTP
• Category: Chat & email

Install

Pick the AI app you use, then copy the settings.

You need

• Runs in the cloudNothing to install; it connects over the internet

Which app do you use?

https://warminboxes.com/mcp

claude mcp add --transport http deliverability-tools https://warminboxes.com/mcp

{
  "mcpServers": {
    "deliverability-tools": {
      "url": "https://warminboxes.com/mcp"
    }
  }
}

{
  "servers": {
    "deliverability-tools": {
      "type": "http",
      "url": "https://warminboxes.com/mcp"
    }
  }
}

https://warminboxes.com/mcp

Your choice stays on this device in a cookie; no account needed.

These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.

What it can do

Tool names and descriptions exactly as the server reported them on Nov 7, 2026. The maker wrote them, not us; we show them as plain text.

• check_deliverability

  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.

• check_spf

  Look up a domain's SPF record and validate it, including the recursive DNS lookup count that silently breaks SPF past 10.

• check_dkim

  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

• check_dmarc

  Look up and parse a domain's DMARC record: policy, subdomain policy, percentage, alignment and reporting tags, each explained. p=none (monitoring) passes: it meets Google and Yahoo's requirement and is fine for broad cold email. p=quarantine is the step for stricter enforcement;

• check_bimi

  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.

• check_mta_sts

  Validate a domain's _mta-sts DNS record and its published policy file: mode, MX patterns, max_age and TLS-RPT.

• check_ssl

  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. ) or a clic

• check_dns

  Query any DNS record type for a domain: MX, TXT, A, AAAA, CNAME, NS, SOA, CAA.

• lookup_txt

  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 mist

• check_rdns

  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

• check_blacklist

  Check a domain or IP against 20+ major email blacklists (Spamhaus, Barracuda, SORBS and others) and report which list it appears on.

• check_surbl

  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.

• check_nameservers

  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.

• check_domain_expiry

  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.

• check_google_domain

  Tell whether a domain is already attached to a Google Workspace account, or is clear for a fresh Google tenant.

• check_cname

  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.

• verify_email

  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.

• lookup_mx

  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`

• segment_esp

  Split a list of domains by the email provider behind them (Google, Microsoft, a security gateway, or another provider) from their MX records. WarmInboxes routes Google-hosted recipients to Google Workspace inboxes and everyone else to Azure; plan_from_list sizes that split.

• plan_from_list

  Estimates a sending fleet for a recipient list. Looks up the MX records of up to 100 recipient domains (or addresses) to measure the provider mix, then sizes a Google Workspace pool for the Google-hosted recipients and an Azure pool for everyone else (Microsoft 365, other provide

• plan_infrastructure

  Estimates how many inboxes and domains a daily cold email volume needs and the monthly cost at WarmInboxes' published prices. Inputs: emailsPerDay; optionally the provider (esp), prewarmed or fresh, billing cycle, emails per inbox per day and inboxes per domain. With currentInbox

• quote_inboxes

  Prices a given number of inboxes at WarmInboxes' published prices: the domains (or Azure tenants) they sit on, daily sending capacity at the provider's pace, monthly cost and delivery time. Use it when the person already knows the count ("preview 100 inboxes"); for a send volume

• get_diagnostic_playbook

  Returns WarmInboxes' diagnostic playbook for a cold email problem: the questions to ask the person, the checks to run in order from cheapest to most expensive (with the tool for each), what WarmInboxes' published studies measured a finding to cost (for example that a SURBL listin

• expand_spintax

  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 se

• generate_unsubscribe

  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.

• check_email_authentication

  SPF, DKIM, DMARC, MX, BIMI and MTA-STS for one domain in one call, each judged pass, weak, fail or not set, with the essentials separated from the optional records. BIMI and MTA-STS are optional and come back "absent", never failed. Use it when someone has been told to "fix their

• check_domain_reputation

  For "this domain used to land and now it does not". Checks the domain against SURBL, its authentication, its age and the address its website resolves to, and returns a verdict by elimination (listed, broken, young, clean or unknown) with what it rules out. No reputation score: re

• check_tracking_domain

  Check the domain a campaign's tracked links point at: whether it resolves, serves a valid certificate, is listed on SURBL, sits on a listed address, belongs under the sending domain, and whether it is a platform's shared tracking host. A listed tracking domain is in the body of e

• check_bulk_sender_requirements

  The bulk sender requirements, sorted honestly: SPF, DKIM, DMARC and MX checked from DNS; forward and reverse DNS when given the sending IP; one-click unsubscribe and From alignment when given a received message's raw headers; and the requirements no outside tool can see (complain

• analyze_headers

  Read a received message's raw headers. Returns the SPF, DKIM and DMARC verdicts the receiver recorded, which domains authenticated and whether they align with the From domain (why DMARC failed on a message that "passed"), the relay hops and delays, the sending IP, plain-English i

• analyze_email_html

  Read an email's HTML. Returns its size against Gmail's ~102 KB clipping limit with what is taking the room, every link and image host, tracking pixels, URL shorteners, and each linked domain checked against SURBL. Parsed inertly: nothing loads, no pixel fires, no link is followed

• analyze_dmarc_report

  Read DMARC aggregate (rua) reports and say who is sending as the domain and what fails: messages passing and failing, failures that are alignment only, quarantined and rejected counts, and each sending IP with its SPF and DKIM outcome, failing senders first. Takes the report XML,

• analyze_cold_email

  Score a cold email's copy 0-100 for spam risk before it is sent: weighted trigger words by category and severity (subject hits weigh extra), ALL-CAPS, links and shorteners, currency and percent-off offers, obfuscated spellings, missing personalisation or opt-out, length. Returns

• audit_campaign

  Audit a cold email campaign before launch: the lead CSV and the sequence checked together for merge tags with no column or empty values, variable syntax the sequencer will not parse, role and disposable addresses, duplicates and too many contacts per company, plus a send forecast

• analyze_bounces

  Classify bounce messages (NDRs): invalid address, full or disabled mailbox, reputation block, authentication failure, throttling, content block or configuration, each with whether it is hard, soft or a block, why it happened and what to do. Separate several bounces with a blank l

• analyze_microsoft_headers

  Read the spam verdict Microsoft 365 or Outlook stamped on a delivered message: SCL (spam confidence), BCL (bulk), PCL, SFV, the category, and the SPF, DKIM, DMARC and composite authentication results, each explained. Use it when mail lands in Outlook junk. For Gmail or any provid

• preview_inbox

  Show how a cold email's sender name, subject line and preview text are cut off in Gmail desktop, Gmail mobile and Outlook, with warnings (no sender name, all caps, empty preview, etc.). Use it to check a subject line fits before sending.

• generate_dns_records

  Write an SPF record from the providers that send for a domain (with an estimate of its DNS lookups against the limit of 10), a DMARC record from a policy, and where a provider publishes DKIM. Returns host, type and value to publish. It writes records; to check what is published,

• plan_rotation

  Suggests a two-batch inbox rotation schedule: the fleet split in half, one batch sending while the other rests, swapped every 1, 2 or 4 weeks. Returns batch sizes, the daily load per active inbox compared with a 15-a-day pace, how many inboxes the volume needs at that pace, and a

• plan_verification_waterfall

  Price an email verification waterfall: the list run through verifiers in sequence with unknowns passed down the chain, every order compared, cheapest cost per usable email first. Uses typical figures for three verifiers unless you pass your own prices and resolve rates (POST JSON

• clean_csv

  Clean a lead CSV: malformed, duplicate, role-based (info@, sales@) and disposable addresses removed, with a count for each reason. Returns the cleaned CSV when it is 500 rows or fewer; a larger file is summarised and the person is sent to the page to download the full result. Doe

• convert_csv

  Rename a lead CSV's columns to the fields a sequencer imports (Instantly, Smartlead, EmailBison, or generic snake_case). Every row and column is kept; only the header changes, and columns with no standard field keep a snake_case name for custom variables. Returns the mapping, and

• combine_csvs

  Merge several lead CSVs into one, matching columns that mean the same thing (Email, email_address, E-mail), optionally removing duplicate emails and adding a column for the file each row came from. Returns the combined CSV when it is 500 rows or fewer. POST JSON: files is an arra

• check_suppression

  Check a campaign list against a do-not-contact list before sending: exact email matches and, optionally, whole suppressed domains, with a per-company cap. Returns what was removed and why, and the clean CSV when it is 500 rows or fewer.

• spamhaus_dbl_guidance

  Explains how to check a domain on the Spamhaus Domain Block List by hand at https://check.spamhaus.org. Does not query the Spamhaus DBL (it needs a paid key) and never returns a listing verdict: the result states that nothing was checked, gives Spamhaus's own lookup, and names th

• burned_inbox_guidance

  Use for "how do I run an inbox placement test", "are my emails landing in spam" or "is my inbox burned". Directs the person to WarmInboxes’ free inbox placement test and Burned Inbox Checker at https://burnedinbox.com, which sends a real test and shows where it lands. This server

• cold_email_writing_resources

  Directs the person to Cold Email AI, the WarmInboxes cold email writing assistant at https://warminboxes.com/AI (a custom GPT on ChatGPT). Does not generate email copy itself; the result gives the link and names the tools here that check a draft (analyze_cold_email, preview_inbox

• find_lead_lists

  Searches WarmInboxes' own catalogue of about 1,000 free B2B lead lists, by industry, role and country, as published at https://warminboxes.com/leads. It does not search the web or any other database. Returns the best-matching lists with lead counts, verified email counts and each

• find_tools

  Find the WarmInboxes free tool for a task ("check my email headers", "clean a CSV", "will this land in spam") and say how to use it: the MCP tool to call here, or the page to send the person to when it runs only in the browser. Call with no task to list every tool.

• find_resources

  Search what WarmInboxes publishes: operator notes (WarmInboxes' rules from running fleets, with the research behind them), cold email guides, deliverability playbooks, original studies and their datasets, costed infrastructure recipes, tool demo videos, inbox guides per sequencer

• read_resource

  Read a WarmInboxes operator note, guide, study, playbook, dataset, recipe, comparison or changelog entry in full, as markdown. Long pages come in parts split at headings: the first call says how many, and nextPart gives the one to ask for. Datasets also return their data as JSON.

• get_pricing

  The WarmInboxes price list as data: prewarmed and fresh inboxes on Google Workspace, Microsoft 365 and Azure, every billing cycle, the safe daily send pace per inbox, and delivery time. For a costed fleet for a volume, use plan_infrastructure.

Basic checksi

We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 8, 2026

• ! Caution

  Maker matches the repo

  The registry lists no source repo, so we cannot match the publisher (warminboxes.com) to the code

• … Not checked yet

  Still maintained

  We have not read this repo from GitHub yet

• … Not checked yet

  Has a licence

  We have not read this repo from GitHub yet

• ✓ Pass

  Endpoint responds

  Responded in 330 ms (HTTP 200)

• – Not applicable

  Sign-in with OAuth

  No sign-in needed

• ✓ Pass

  No hidden instructions in tool descriptions

  Read 52 tool descriptions and found no hidden instructions to the AI

Compared with others in Chat & emaili

• More stars than 0% of the other 1850 servers in this category
• Published to the registry more recently than 65% of the other 1850 servers in this category
• Basic checks equal to or better than 45% of the other 1850 servers in this category

Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.

Alternatives

Servers in the same category from other makers, sorted by stars.

Reading a card:↓ Downloads per weeki★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi

README from the maker

No README found in the repo