MailX

mailX is a free toolkit for diagnosing email deliverability and DNS problems. Entering a domain runs live checks across DNS records, SPF, DKIM, DMARC, BIMI, MX configuration, blacklist status, and SMTP or IMAP connectivity, then returns a report that explains each issue in plain language along with the specific fix. Every tool queries live DNS in real time and none require a signup or account, which makes the suite usable for quick one-off diagnostics as well as routine audits. Beyond the browser interface, the same checks are exposed through a JSON API and an MCP server, so scripts and AI agents can run them programmatically. mailX is published by the team behind Mailwarm and states that more than 50,000 marketers and developers use the tools.

Features

• Combined Deliverability Audit: Runs SPF, DKIM, DMARC, MX, and blacklist checks together in one pass and returns a single consolidated report.
• Authentication Checkers: Individual SPF, DKIM, DMARC, and BIMI validators that explain failures without requiring the user to read raw records.
• DNS Lookup Suite: A, MX, TXT, CNAME, and PTR lookups alongside a DNS checker and a propagation checker.
• Mail Server Testing: SMTP and IMAP tests and finders that check connectivity, configuration, and response time.
• Record Generators: SPF, DMARC, DKIM, and general DNS record generators sit next to the checkers so flagged problems can be fixed immediately.
• API and MCP Access: A JSON API and an MCP server allow the same checks to run inside automations, CI pipelines, or AI agents.

Pricing

mailX publishes no paid plans. The tools are offered free of charge:

• All tools: $0. Every checker, lookup, generator, and the full deliverability audit run without a signup, account, or credit card.

The company also offers a booked consultation for teams whose mail is already landing in spam. Scope and pricing for that service are Contact for details.

Pros

• Free With No Signup: Every check runs without an account, which removes the friction of one-off diagnostics during an incident.
• Consolidated Audit: Authentication, DNS, and blacklist checks run together instead of being stitched together from several single-purpose sites.
• Plain-Language Output: Results explain what is broken and how to fix it rather than returning raw record dumps.
• Generators Beside Checkers: SPF, DKIM, and DMARC generators sit alongside the validators, so a flagged issue can be corrected in the same session.
• Agent and Script Friendly: The JSON API and MCP server make the toolkit usable inside automations and AI workflows, not just the browser.
• Live Results: Checks query live DNS in real time rather than returning cached lookups.

Cons

• Diagnostics Only: The toolkit identifies problems but does not warm up mailboxes, send email, or remediate anything on the user's behalf.
• No Saved History: With no accounts, reports are not stored, so changes cannot be compared between checks over time.
• No Monitoring or Alerts: Checks are run on demand rather than watching a domain continuously and flagging regressions.
• Configuration, Not Placement: The tools verify authentication and blacklist status rather than testing where messages actually land across providers.
• Undefined Paid Support: Help beyond the free tools runs through a booked call with no published scope or pricing.