--- title: "WarmInboxes Deliverability Agent for Claude and ChatGPT" description: "The WarmInboxes Deliverability Agent: free cold email diagnostics inside Claude, ChatGPT and any MCP client. SPF, DKIM, DMARC, blocklists, Outlook SCL…" url: https://warminboxes.com/plugins/deliverability-agent breadcrumb: "Home > Agents > Deliverability Agent" --- [WarmInboxes agents](https://warminboxes.com/plugins) # Deliverability Agent Ask why cold email stopped landing and get an answer from live checks rather than a guess: authentication records, blocklists, domain setup, the headers of a message that went to junk, a bounce, the copy and the list. It says what it could not check, and when the infrastructure itself is the problem it says that too. For anyone whose cold email results dropped, or who wants to know a domain is ready before it sends. - Claude: [Add to Claude](https://claude.ai/customize/connectors?modal=add-custom-connector&connectorName=WarmInboxes&connectorUrl=https%3A%2F%2Fwarminboxes.com%2Fmcp) `https://warminboxes.com/mcp` (Submitted for review) - ChatGPT: [Add to ChatGPT](https://chatgpt.com/plugins) `https://warminboxes.com/mcp` (Submitted for review). ChatGPT: turn on developer mode (Settings, Apps & Connectors, Advanced settings), then Add, Custom MCP server, paste the URL, Authentication: none. - Grok: [Add to Grok](https://grok.com/connectors) `https://warminboxes.com/mcp` (Works as a custom connector). Grok: Connectors, New Connector, Custom, paste the URL, no authentication. Custom connectors are on Grok’s paid plans. - Claude Code: Copy the command `claude mcp add --transport http warminboxes https://warminboxes.com/mcp` (Works today) - Cursor, VS Code and other MCP clients: Copy the server URL `https://warminboxes.com/mcp` (Streamable HTTP, no authentication) ## What to ask it These 41 prompts are our test suite: each names the tool that answers it, and we rerun every one after each change to the agent. ### Authentication - "Check my SPF for stripe.com" `check_spf` - "Is DKIM set up on stripe.com?" `check_dkim` - "What does the DMARC record on stripe.com do?" `check_dmarc` - "Check SPF, DKIM and DMARC for stripe.com in one go" `check_email_authentication` - "Do I need BIMI on stripe.com?" `check_bimi` - "Does stripe.com have MTA-STS?" `check_mta_sts` ### Domains - "Is stripe.com set up properly to send cold email?" `check_deliverability` - "Am I on any blacklists? My domain is stripe.com" `check_blacklist` - "Does stripe.com meet the Gmail and Yahoo bulk sender rules?" `check_bulk_sender_requirements` - "Is my tracking domain track.stripe.com set up right?" `check_tracking_domain` - "Who hosts email for stripe.com?" `lookup_mx` - "When does stripe.com expire?" `check_domain_expiry` - "Is stripe.com on SURBL?" `check_surbl` - "Does 8.8.8.8 have reverse DNS?" `check_rdns` ### Diagnosis - "Why did my reply rate fall? We send from stripe.com" `check_domain_reputation` - "My emails show SCL 5 in Outlook. What does that mean? (headers pasted)" `analyze_microsoft_headers` - "Read these email headers and tell me if it passed authentication" `analyze_headers` - "What does this bounce mean? 550 5.7.1 Message rejected as spam" `analyze_bounces` - "Make sense of this DMARC aggregate report XML" `analyze_dmarc_report` ### Honest limits - "Is stripe.com on the Spamhaus DBL?" `spamhaus_dbl_guidance` - "Am I burned?" `burned_inbox_guidance` - "Write my cold email for me" `cold_email_writing_resources` - "Will fixing DMARC guarantee I land in the inbox?" `find_resources` ### Copy - "Check this cold email for spam words" `analyze_cold_email` - "How does this subject line cut off in Gmail on a phone?" `preview_inbox` - "Will Gmail clip this HTML email?" `analyze_email_html` - "Check my spintax renders: {Hi|Hello} {{first_name}}" `expand_spintax` - "Write me a CAN-SPAM unsubscribe footer for Acme" `generate_unsubscribe` ### Lists - "Clean this lead list: remove duplicates and role addresses" `clean_csv` - "Convert this CSV to Smartlead’s import format" `convert_csv` - "Combine these two lead CSVs and dedupe them" `combine_csvs` - "Remove anyone on my do-not-contact list from this CSV" `check_suppression` - "Audit this campaign before I send it" `audit_campaign` - "Which of these domains are on Google and which on Microsoft? stripe.com, microsoft.com" `segment_esp` ### Setup - "Write the SPF and DMARC records for Google Workspace" `generate_dns_records` ### Research - "Which top-level domain should I buy for cold email?" `find_resources` - "Does a SURBL listing actually hurt cold email replies?" `find_resources` - "Is there a free tool to check my BIMI logo?" `find_tools` - "Find me a lead list of SaaS founders" `find_lead_lists` ### Pricing - "How much do your inboxes cost?" `get_pricing` - "How many inboxes do I need to send 1,000 cold emails a day?" `plan_infrastructure` ## What an answer looks like "My emails show SCL 5 in Outlook. What does that mean? (headers pasted)" `analyze_microsoft_headers`: SCL 5: classified as spam, which default Microsoft policy delivers to Junk. Then each signal in turn (SPF, DKIM, DMARC, composite authentication, the spam filter verdict), so the one that did the damage stands out. "Is stripe.com on the Spamhaus DBL?" `spamhaus_dbl_guidance`: Not checked: the Spamhaus DBL needs a paid query key, so nothing here says the domain is listed or clean. It links Spamhaus’s own free lookup and offers the blocklists it does query. "Am I burned?" `burned_inbox_guidance`: Sends you to the free Burned Inbox Checker, and offers the reputation and deliverability checks that rule the domain in or out. *If it is confirmed burned, the Cold Email Infrastructure Agent can size a replacement.* ## Exactly what it can do ### Authentication - [SPF, DKIM, DMARC, MX, BIMI and MTA-STS together](https://warminboxes.com/email-authentication-checker) `check_email_authentication` - [SPF record](https://warminboxes.com/spf-checker) `check_spf` - [DKIM record](https://warminboxes.com/dkim-checker) `check_dkim` - [DMARC record](https://warminboxes.com/dmarc-checker) `check_dmarc` - [BIMI record](https://warminboxes.com/bimi-checker) `check_bimi` - [MTA-STS policy](https://warminboxes.com/mta-sts-checker) `check_mta_sts` - [SPF and DMARC record generator](https://warminboxes.com/record-generator) `generate_dns_records` ### Domains and reputation - [Deliverability grade (A-F)](https://warminboxes.com/deliverability-checker) `check_deliverability` - [Is the domain the problem (by elimination)](https://warminboxes.com/domain-reputation-checker) `check_domain_reputation` - [Blacklist / RBL check](https://warminboxes.com/blacklist-checker) `check_blacklist` - [SURBL URI blacklist (bulk)](https://warminboxes.com/surbl-checker) `check_surbl` - [Gmail, Yahoo and Microsoft bulk sender requirements](https://warminboxes.com/bulk-sender-requirements-checker) `check_bulk_sender_requirements` - [Click-tracking domain](https://warminboxes.com/tracking-domain-checker) `check_tracking_domain` - [Domain registration and expiry](https://warminboxes.com/domain-expiry-checker) `check_domain_expiry` - [Google Workspace tenancy](https://warminboxes.com/google-domain-checker) `check_google_domain` ### DNS - [DNS records](https://warminboxes.com/dns-checker) `check_dns` - [MX records and mail provider](https://warminboxes.com/mx-lookup) `lookup_mx` - [TXT records, identified](https://warminboxes.com/txt-record-lookup) `lookup_txt` - [CNAME chain](https://warminboxes.com/cname-checker) `check_cname` - [Nameservers and DNS provider (bulk)](https://warminboxes.com/nameserver-checker) `check_nameservers` - [Reverse DNS and forward confirmation](https://warminboxes.com/reverse-dns-lookup) `check_rdns` - [TLS certificate](https://warminboxes.com/ssl-checker) `check_ssl` ### Messages that went wrong - [Email headers: auth, alignment, one-click unsubscribe](https://warminboxes.com/dmarc-alignment-checker) `analyze_headers` - [Microsoft spam verdict (SCL)](https://warminboxes.com/scl-analyzer) `analyze_microsoft_headers` - [Bounce messages explained](https://warminboxes.com/bounce-analyzer) `analyze_bounces` - [DMARC aggregate reports](https://warminboxes.com/dmarc-report-analyzer) `analyze_dmarc_report` - [Email HTML: Gmail clipping, links, pixels](https://warminboxes.com/gmail-clipping-checker) `analyze_email_html` ### Copy - [Cold email spam check](https://warminboxes.com/spam-checker) `analyze_cold_email` - [Inbox preview (truncation)](https://warminboxes.com/inbox-previewer) `preview_inbox` - [Spintax and merge tag preview](https://warminboxes.com/spintax-tester) `expand_spintax` - [CAN-SPAM opt-out footer](https://warminboxes.com/unsubscribe-generator) `generate_unsubscribe` ### Lists - [Lead CSV cleaner](https://warminboxes.com/csv-cleaner) `clean_csv` - [Sequencer CSV converter](https://warminboxes.com/sequencer-csv-converter) `convert_csv` - [Combine lead CSVs](https://warminboxes.com/csv-combiner) `combine_csvs` - [Suppression list check](https://warminboxes.com/suppression-checker) `check_suppression` - [Pre-send campaign audit](https://warminboxes.com/pre-send-checker) `audit_campaign` - [ESP segmentation (bulk)](https://warminboxes.com/esp-segmenter) `segment_esp` - [Email verification (bulk)](https://warminboxes.com/email-verifier) `verify_email` ### Planning - [Inboxes and domains for a send volume (estimate)](https://warminboxes.com/calculator) `plan_infrastructure` - Price a number of inboxes (quote) `quote_inboxes` - [Fleet estimate from a recipient list](https://warminboxes.com/esp-calculator) `plan_from_list` - [Inbox rotation schedule (suggested)](https://warminboxes.com/inbox-rotation-planner) `plan_rotation` - [Email verification waterfall](https://warminboxes.com/waterfall-calculator) `plan_verification_waterfall` - Price list `get_pricing` ### Research and finding things - Guides, playbooks, studies and videos `find_resources` - Read a guide or study `read_resource` - Free tool for a job `find_tools` - Free B2B lead lists (WarmInboxes catalogue) `find_lead_lists` ### Hand-offs, which run nothing - [Spamhaus DBL guidance (not queried)](https://warminboxes.com/spamhaus-checker) `spamhaus_dbl_guidance` - Burned Inbox Checker guidance `burned_inbox_guidance` - Cold email writing resources `cold_email_writing_resources` ## What it will not do - Every tool is read-only. It does not send email, buy inboxes or change DNS. - The Spamhaus DBL needs a paid key and is not queried. Asked about it, the answer says "not checked" and links Spamhaus’s own lookup; it never reports a domain as clean there. - There are no reputation scores: Gmail and Microsoft keep those private, so the reputation check works by elimination and says so. - It cannot test inbox placement or open an SMTP connection, because outbound port 25 is blocked where it runs. Email verification is syntax, domain and MX, not a mailbox probe. - Passing authentication does not mean a message will land; it removes the reasons it would not. - A free daily limit applies, counted in distinct domains. Pasted headers, copy and CSVs are processed to answer and not stored. ## When it sends you to the Infrastructure Agent A domain is on a domain-level blocklist, on IP blocklists, grades D or F, or a burned inbox is confirmed. *"This infrastructure appears degraded. Fix what can be fixed on it first; if it has to be replaced, the Cold Email Infrastructure Agent can size the replacement."* [The WarmInboxes Cold Email Infrastructure Agent](https://warminboxes.com/plugins/cold-email-infrastructure-agent) ## How the answers are worked out - [How the deliverability grade is worked out](https://warminboxes.com/deliverability-checker): The weights behind the A-F grade. - [Domain reputation, by elimination](https://warminboxes.com/domain-reputation-checker): Why there is no score, and what is checked instead. - [Which blocklists are checked](https://warminboxes.com/blacklist-checker): The list, and why Spamhaus DBL is not on it. - [Reading Microsoft’s SCL](https://warminboxes.com/scl-analyzer): What each SCL value and SFV verdict means. - [Our placement research](https://warminboxes.com/research): The studies the research answers quote. ## Questions ### Is the WarmInboxes Deliverability Agent free? Yes. No account, no API key and no sign-in. A daily limit counted in distinct domains keeps it fair; re-checking a domain the same day is free. ### Is it approved in the Claude and ChatGPT directories? WarmInboxes was submitted to the Claude Connectors Directory on 22 October 2026 and is in review. Until it is listed, add it to Claude yourself in a minute: it is the same server, and it works the same way. WarmInboxes was submitted to the ChatGPT plugin directory on 23 October 2026 and is in review. Until it is listed, add it to ChatGPT yourself in a minute: it is the same server, and it works the same way. ### How is it different from the Infrastructure Agent? The Deliverability Agent finds out what is wrong; the Infrastructure Agent works out what to buy. This one has every free tool, including the sizing ones; the Infrastructure Agent has only sizing, pricing and setup, for someone planning a fleet. ### Can it buy inboxes? No. Every tool is read-only. It works out what to order and what it costs; the first order is placed in the WarmInboxes app, and existing customers can connect the separate purchasing server from a client that sends an API key header. ### What does it store? Pasted headers, copy and CSVs are processed to answer and not stored. For the daily limit it keeps the domains checked that day, deleted within two days, and it counts sessions and tool calls anonymously, with no domain, IP or user id, for 90 days. The privacy policy has the detail. [WarmInboxes Cold Email Infrastructure Agent](https://warminboxes.com/plugins/cold-email-infrastructure-agent) · [All agents](https://warminboxes.com/plugins) · [For AI Agents](https://warminboxes.com/for-ai) · [Developers](https://warminboxes.com/developers) · [Privacy](https://warminboxes.com/privacy)