Mailwarm

mailX is a deliverability toolkit from Mailwarm (YC S20). It checks domain and email configuration to explain why messages land in spam and how to fix them. People can use it directly, or developers and AI agents can call it through an API or MCP server. It checks configuration only and does not send email itself.

Key features

• Spam-placement diagnostics
• Email authentication checks
• Fix recommendations
• API access
• MCP server

Pricing

mailX is free to use. Prices checked on the official pricing page in October 2026 and may change.

Who it's for

mailX is used by marketers, sales teams, developers and startups.