mailX

mailX is a free email deliverability and DNS diagnostics toolkit. It checks why emails land in spam and explains how to fix it, covering SPF, DKIM, DMARC, BIMI, MX, blacklist status, and SMTP/IMAP configuration. The same tools are accessible to people through the website and to AI agents through an MCP server and JSON API.

What It Is

mailX is a collection of free, no-signup tools that run against live DNS in real time. It groups them into authentication checks (SPF, DKIM, DMARC, BIMI), deliverability checks (blacklist scanning, SMTP and IMAP testing, SMTP/IMAP finders), DNS lookups (A, MX, TXT, CNAME, PTR, full DNS, propagation), and record generators (SPF, DMARC, DKIM, DNS records). A combined audit can run SPF, DKIM, DMARC, MX, and blacklist checks in one pass and return a single report. The site says results come with plain-English explanations and specific fixes rather than only raw records or a score.

How It Works

The homepage describes a three-step flow: enter a domain or IP, mailX analyzes the DNS, authentication, MX, blacklist, and infrastructure setup, and then returns a report listing issues and exact steps to fix them. The about page frames deliverability as a system spanning domain reputation, DNS setup, authentication, sending history, content, engagement, and mailbox provider rules, and positions the tools as a way to make that system easier to interpret.

Built for Humans and AI Agents

A defining feature is that every tool is exposed to AI agents, not just the web UI. The docs state mailX runs an MCP (Model Context Protocol) server at a single HTTP endpoint using Streamable HTTP and JSON-RPC 2.0, with no authentication required. Agents can list and call tools such as SPF, DKIM, DMARC, and blacklist checks, and the server also publishes one-click prompts (an audit-deliverability workflow and a setup-dns workflow) and an Agent Skill that teaches agents how and when to use the tools. The documentation provides setup instructions for Claude, ChatGPT, Cursor, VS Code, Windsurf, Zed, the OpenAI Agents SDK, and the Anthropic Messages API.

Who It Is For

The site lists founders running cold email or transactional flows, sales teams scaling outbound, marketing teams managing campaigns and lifecycle messaging, agencies handling multiple client domains, and developers debugging DNS, SMTP, and authentication records. It also publishes guides on deliverability, DNS, email authentication, and why emails go to spam.

Part of the Mailwarm Ecosystem

The about page states mailX is a brand operated by Mailwarm Inc., positioned as the diagnostic layer of a wider set of products. It sits alongside Mailwarm, described as an email warmup tool for building sender reputation, and MailAdept, described as a subscription deliverability service. mailX itself is the free, on-demand checking layer.