--- title: "WarmInboxes ChatGPT Plugin for Cold Email Deliverability" description: "Add WarmInboxes to ChatGPT: free cold email deliverability checks, copy and list tools, inbox planning and our placement research, as a plugin with no account…" url: https://warminboxes.com/chatgpt-plugin breadcrumb: "Home > For AI Agents > ChatGPT plugin" --- ChatGPT plugin # WarmInboxes for ChatGPT A ChatGPT plugin for cold email: check whether a domain is ready to send, score a draft for spam triggers, clean and convert lead lists, read why a message went to junk, size the inboxes a volume needs, and quote our own placement research. Free, read-only, no account. Submitted for review 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. ## Add it to ChatGPT Custom MCP servers need developer mode, on the ChatGPT plans that offer it. - Turn on developer mode in ChatGPT: Settings, Apps & Connectors, Advanced settings. ChatGPT only accepts custom servers with it on. - Click Add to ChatGPT. ChatGPT opens on Plugins, and the server URL is copied. - Click Add, choose Custom MCP server, and fill it in with the values below. Authentication: none. - In a chat, add WarmInboxes from the tools menu and ask, for example, "Is stripe.com set up properly to send cold email?" - Name: `WarmInboxes` - Description: `Free cold email deliverability checks` - MCP server URL: `https://warminboxes.com/mcp` - Authentication: `No authentication` [Add to ChatGPT →](https://chatgpt.com/plugins) ## What to ask it ### Domains - "Is stripe.com set up properly to send cold email?" `check_deliverability` - "Check the SPF, DKIM and DMARC records for mydomain.com." `check_email_authentication` - "Is mydomain.com on any blacklists?" `check_blacklist` ### Copy - "Check this cold email for spam words: (paste the draft)" `analyze_cold_email` - "How will this subject line and opening cut off in Gmail on a phone?" `preview_inbox` ### Lists - "Clean this lead list and remove duplicates and role addresses: (paste the CSV)" `clean_csv` - "Which of these domains are on Google and which on Microsoft?" `segment_esp` - "Convert this CSV to Smartlead’s import format." `convert_csv` ### Diagnosis - "Why did this email land in Outlook junk? (paste the headers)" `analyze_microsoft_headers` - "What does this bounce mean, and should I keep sending? (paste it)" `analyze_bounces` ### Planning - "How many inboxes and domains do I need to send 1,000 cold emails a day?" `plan_infrastructure` - "Plan a rotation for 60 inboxes sending 600 a day." `plan_rotation` ### Research - "Does a SURBL listing actually hurt cold email replies?" `find_resources, read_resource` - "Which top-level domain should I buy for cold email?" `find_resources, read_resource` ## What it will not do - Every tool is read-only. It does not send email, buy inboxes or change your 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. - Authentication checks cannot guarantee inbox placement, and there are no invented reputation scores: mailbox providers keep those private. - A free daily limit applies, counted in distinct domains. Checking a domain again the same day does not count again. - Pasted copy, headers and CSVs are processed to answer and not stored. ## When the answer is more inboxes Ask ChatGPT how many inboxes a send volume needs and it works out the count, the domains and the monthly cost from our prices. The first order is placed in the WarmInboxes app; prewarmed Google, Microsoft 365 and Azure inboxes arrive set up and ready to connect to your sequencer. [See the inboxes](https://warminboxes.com/offer). ## Questions ### Is the WarmInboxes ChatGPT plugin 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 for ChatGPT yet? 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. ### What does it see, and is anything stored? It sees what you ask it to check: a domain, an address, or text you paste such as headers, a draft or a CSV. Domains are looked up live. Pasted text is processed to answer and not stored. The privacy policy has the detail. ### Can it buy inboxes or change my DNS? No. Every tool is read-only. When the answer is more inboxes, 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. ### Does it work outside ChatGPT? Yes. It is a standard remote MCP server at https://warminboxes.com/mcp, so Claude, ChatGPT, Grok, Claude Code, Cursor, VS Code and other MCP clients can all use it. [WarmInboxes for Claude](https://warminboxes.com/claude-connector) · [For AI Agents](https://warminboxes.com/for-ai) · [Privacy](https://warminboxes.com/privacy)