Unlimited Messaging sends WhatsApp messages, emails and SMS to your customers from your own accounts: your own WhatsApp number (linked by QR code), your own mailbox (IMAP/SMTP: Gmail or your domain) and your own Android phone (SMS from its SIM through a free open source app). One REST API request can go out on all three channels.
There is no per-message billing: every plan, the free one included, sends unlimited messages. Paid plans (Medium 19 EUR/month, Max 29 EUR/month) remove the "Sent with UnlimitedMessaging.app" footer and add media, webhooks, higher throughput and support.
Four ways to use it: a hosted MCP server (https://mcp.unlimitedmessaging.app) so Claude, ChatGPT or Cursor can send and read WhatsApp, email and SMS in plain words; a REST API with TypeScript and Python SDKs; an n8n community node; and a no-code web app with an inbox for replies. EU-hosted and GDPR-compliant.
WhatsApp goes through a linked device on your normal account, not Meta's official Business API: no template approval and no per-message fee, but sending spam can get a number banned.