Mailx
mailX is a free email deliverability and DNS diagnostic toolkit that helps teams see why emails hit spam and how to fix technical issues. It combines live DNS lookups, SPF, DKIM, DMARC and blacklist checks with clear, human readable guidance. Both humans and AI agents can run audits in seconds from the browser, an API or an MCP server.
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Pricing
- Free Tool Access: DNS lookups, deliverability tests, blacklist checks and record generators are currently offered free of charge with no account required.
- Consulting-style Help: A “SOS I Land in SPAM” option connects users with a human expert, although public per session or subscription pricing is not clearly listed.
Features
- Combined deliverability audit: Runs SPF, DKIM, DMARC, MX and blacklist checks together for a domain or IP and returns one prioritized report.
- Real time DNS and mail server tools: Provides DNS lookup, propagation checks, MX, TXT, CNAME and PTR queries, plus SMTP and IMAP tests and SPF/DMARC/DKIM generators built on live DNS.
- Plain language issue explanations: Translates dense DNS and authentication details into short descriptions and copy paste ready records so non specialists can correct problems quickly.
- MCP and JSON API for AI agents: Exposes each checker and a higher level deliverability audit through an MCP server and JSON responses that tools and agents can call programmatically.
Use cases
- Founders & Indie Builders: Checking domains for cold email, newsletters and transactional systems before scaling volume.
- Sales & SDR Teams: Verifying sender domains and fixing technical issues that quietly reduce reply rates in outbound campaigns.
- Marketing & Growth Teams: Auditing DNS and authentication across marketing automation, CRM and lifecycle messaging domains.
- Agencies & Deliverability Consultants: Running quick multi domain audits for clients and producing clear, shareable DNS fix lists.
- Developers & DevOps Engineers: Debugging DNS, SMTP and IMAP configuration issues without jumping between many small utilities.
- AI Agent Builders: Giving agents an MCP skill for live SPF, DKIM, DMARC and blacklist checks inside larger workflows.
- Uncommon Use Cases: Utilized by security teams for fast spoofing and misconfiguration checks; Adopted by technical educators for teaching DNS and email authentication with live examples.