If you’re building agents that need to read and send email, you’ve probably hit the limits of typical email APIs: they’re stateless, focused on sending, and don’t give you threads, history, or content that’s easy for an LLM to use. NornWeave is an open-source, self-hosted Inbox-as-a-Service API built for that use case. It adds a stateful layer (virtual inboxes, threads, full history) and an intelligent layer (HTML→Markdown parsing, threading, optional semantic search) so your agents can consume email via REST or MCP instead of raw webhooks and HTML.

You get virtual inboxes per agent, webhook ingestion from SMTP/IMAP, Mailgun, SES, SendGrid, or Resend, and an MCP server that plugs into Claude, Cursor, and other MCP clients with tools like create_inbox, send_email, search_email, and wait_for_reply. Threads are returned in an LLM-friendly format (e.g. role/author/content), and you can self-host on your own infra. If your agents need to own an inbox and hold context across messages, NornWeave is worth a look.