MCP server that sends mail over SMTP, gated behind an allowlist and a human confirmation
To add SMTP to Claude, run the install command below or copy the ready-made config for Claude Code, Claude Desktop, Cursor and VS Code further down. Restart your client after adding it and its tools show up in your next conversation. It needs 20 environment variables, listed below.
Install
npx -y @ni-c/smtp-mcp@0.2.0Environment variables
SMTP_HOSTSet in your MCP configSMTP_PORTSet in your MCP configSMTP_TLSSet in your MCP configSMTP_USERSet in your MCP configSMTP_PASSWORDSet in your MCP configSMTP_FROMSet in your MCP configSMTP_REPLY_TOSet in your MCP configSMTP_ALLOW_SENDSet in your MCP configSMTP_ALLOWED_RECIPIENTSSet in your MCP configSMTP_MAX_RECIPIENTSSet in your MCP configSMTP_MAX_SENDS_PER_HOURSet in your MCP configSMTP_MAX_MESSAGE_BYTESSet in your MCP configSMTP_MAX_ATTACHMENT_BYTESSet in your MCP configSMTP_ATTACHMENT_DIRSet in your MCP configSMTP_ATTACHMENT_TYPESSet in your MCP configSMTP_SIGNATURESet in your MCP configSMTP_AUDIT_LOGSet in your MCP configSMTP_ALLOW_TOOLSSet in your MCP configSMTP_DENY_TOOLSSet in your MCP configSMTP_INSECURE_TLSSet in your MCP configInstall with your client
claude mcp add smtp --env SMTP_HOST=<YOUR_SMTP_HOST> --env SMTP_PORT=<YOUR_SMTP_PORT> --env SMTP_TLS=<YOUR_SMTP_TLS> --env SMTP_USER=<YOUR_SMTP_USER> --env SMTP_PASSWORD=<YOUR_SMTP_PASSWORD> --env SMTP_FROM=<YOUR_SMTP_FROM> --env SMTP_REPLY_TO=<YOUR_SMTP_REPLY_TO> --env SMTP_ALLOW_SEND=<YOUR_SMTP_ALLOW_SEND> --env SMTP_ALLOWED_RECIPIENTS=<YOUR_SMTP_ALLOWED_RECIPIENTS> --env SMTP_MAX_RECIPIENTS=<YOUR_SMTP_MAX_RECIPIENTS> --env SMTP_MAX_SENDS_PER_HOUR=<YOUR_SMTP_MAX_SENDS_PER_HOUR> --env SMTP_MAX_MESSAGE_BYTES=<YOUR_SMTP_MAX_MESSAGE_BYTES> --env SMTP_MAX_ATTACHMENT_BYTES=<YOUR_SMTP_MAX_ATTACHMENT_BYTES> --env SMTP_ATTACHMENT_DIR=<YOUR_SMTP_ATTACHMENT_DIR> --env SMTP_ATTACHMENT_TYPES=<YOUR_SMTP_ATTACHMENT_TYPES> --env SMTP_SIGNATURE=<YOUR_SMTP_SIGNATURE> --env SMTP_AUDIT_LOG=<YOUR_SMTP_AUDIT_LOG> --env SMTP_ALLOW_TOOLS=<YOUR_SMTP_ALLOW_TOOLS> --env SMTP_DENY_TOOLS=<YOUR_SMTP_DENY_TOOLS> --env SMTP_INSECURE_TLS=<YOUR_SMTP_INSECURE_TLS> -- npx -y @ni-c/smtp-mcp@0.2.0
Run this in a terminal to add the server to Claude Code.
What this does
SMTP exposes a set of tools to Claude over the Model Context Protocol. After you add it to claude_desktop_config.json (snippet above) and restart Claude Desktop, those tools become callable inside any conversation.
Requirements
This server needs the following environment variables to be set before it can run:
SMTP_HOST SMTP_PORT SMTP_TLS SMTP_USER SMTP_PASSWORD SMTP_FROM SMTP_REPLY_TO SMTP_ALLOW_SEND SMTP_ALLOWED_RECIPIENTS SMTP_MAX_RECIPIENTS SMTP_MAX_SENDS_PER_HOUR SMTP_MAX_MESSAGE_BYTES SMTP_MAX_ATTACHMENT_BYTES SMTP_ATTACHMENT_DIR SMTP_ATTACHMENT_TYPES SMTP_SIGNATURE SMTP_AUDIT_LOG SMTP_ALLOW_TOOLS SMTP_DENY_TOOLS SMTP_INSECURE_TLS
Set these via the env object in your MCP config (see claude_desktop_config.json snippet above).
Frequently asked questions
How do I install SMTP?
Run the Claude Code command in the install section to add SMTP to Claude Code, or copy the ready-made config for your client from the install section on this page. Restart your client afterwards and the tools appear in your next conversation.
Which clients work with SMTP?
This page carries setup and config for Claude Code, Claude Desktop, Cursor and VS Code. Any other MCP client that accepts a standard server config can connect to SMTP as well.
Does SMTP need an API key?
Yes. Before it can run, set these environment variables: SMTP_HOST, SMTP_PORT, SMTP_TLS, SMTP_USER, SMTP_PASSWORD, SMTP_FROM, SMTP_REPLY_TO, SMTP_ALLOW_SEND, SMTP_ALLOWED_RECIPIENTS, SMTP_MAX_RECIPIENTS, SMTP_MAX_SENDS_PER_HOUR, SMTP_MAX_MESSAGE_BYTES, SMTP_MAX_ATTACHMENT_BYTES, SMTP_ATTACHMENT_DIR, SMTP_ATTACHMENT_TYPES, SMTP_SIGNATURE, SMTP_AUDIT_LOG, SMTP_ALLOW_TOOLS, SMTP_DENY_TOOLS, SMTP_INSECURE_TLS. They go in the env block of your MCP config.
Imported from the Official MCP Registry. The details above come from the registry entry; the maker can claim this listing to correct them, add docs, and see its traffic.
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