InboxWall: local-first MCP server sanitizes email HTML to block prompt injection

InboxWall is an open-source MCP server that sanitizes email HTML before an AI agent sees it, stripping CSS, JavaScript, hidden text, zero-width and directional Unicode characters, HTML comments and risky attributes. It runs entirely on the local machine with no cloud service or API keys, while the calling agent fetches mail via IMAP or a mail API.

• Strips CSS, JavaScript, HTML comments and attributes like data URIs and srcdoc
• Removes zero-width characters, directional overrides and variation selectors
• Runs locally, so email content never leaves the device
• Keeps only p, a, br, strong, em, ul, li, blockquote tags and href