SMTP

io.github.ni-c/smtp-mcpv0.2.0Email

MCP server that sends mail over SMTP, gated behind an allowlist and a human confirmation

The current version, v0.2.0, was published to the official MCP registry on 2026-09-07. It is distributed as @ni-c/smtp-mcp on npm and as the Docker image ghcr.io/ni-c/smtp-mcp:0.2.0, filed under Email by this index, and declares 20 environment variables. Removals and unreachable sources are measured across every server this index tracks, contract drift across the servers that answer in consecutive snapshots; the index's current counts put this record in context.

In-path gate · all MCP tools

Using SMTP in Claude, Cursor, Gemini CLI, Cline, or Zed?

MCP tool contracts can change remotely with no version bump. The mcpindex gate pins each contract and HOLDs the call when it drifts-before your agent acts. Zero credentials. This is not the package install for this server itself (use Install this server for that).

Install the mcpindex gate (one command)

Rewrites your MCP host config so each server launches behind the gate. Inspect first: curl -fsSL https://mcpindex.ai/install.sh | less

uv tool install mcpindex-gate && mcpindex-config-wire

Auditable install path →Watch it hold a drift →

Trust verdict · v1 advisory · method

REVIEWstatus: PARTIALfresh until 2026-10-26 17:03 UTC

screened 2026-09-04tier: scannedgranularity: description-levelsource: registry

Semantic screen found no manipulation pattern in the description. Conformance probe not yet run.

mcpindex.integrity.descriptionpassINFO

evidence“Normal mail sending capability”via static_description

Limits of this verdict

- Semantic screen only - the deterministic conformance probe has not run on this server
- Confidence is reported but not yet calibrated (v1)
- Screen reads the tool description, not the live behavior
- advisory
- registry description only no input schema
- screen model 8b
- Still current: the description we screened is unchanged, re-checked against the registry
- The registry listing (version, packages, links) changed after this screen ran - the description we assessed did not

Semantic screen: an LLM judge reads the tool description for hidden instructions (status PARTIAL). A pass means the description is not lying, not that the tool is safe: a high-capability tool with an honest description still warrants caution. The deterministic conformance probe has not been run on this server yet, so the screen here is semantic-only. Posture: advisory. Confidences are reported but not yet calibrated (calibrated=false at v1). Full verdict history is not shown on this page.

Own this server? Test a description on the public screen → It is a separate check from the verdict above, so the two can differ.

That verdict was true at screening time (snapshot 2026-10-19).

Contracts can change after screening, with no version bump. The gate pins SMTP’s tool contracts on first sight and holds any silent change before your agent acts - the check that keeps being true on Tuesday.

See your first HOLD in 2 minutes →

Cite this record

People vet a server before wiring it in. One line on your project site or docs answers that with an independent record: screening verdict, registry provenance, contract drift history. It stays current as new screens and drift events land.

Markdown

[Independent trust record for SMTP](https://mcpindex.ai/server/io-github-ni-c-smtp-mcp) - screening verdict, registry provenance, and contract drift monitoring.

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<a href="https://mcpindex.ai/server/io-github-ni-c-smtp-mcp">Independent trust record for SMTP</a> - screening verdict, registry provenance, and contract drift monitoring.

Embed this badge

A live verdict badge for your README or listing. It reflects the current screen, links back here, and updates when the verdict does.

Markdown

[![mcpindex](https://mcpindex.ai/api/v1/badge/io-github-ni-c-smtp-mcp)](https://mcpindex.ai/server/io-github-ni-c-smtp-mcp)

HTML

<a href="https://mcpindex.ai/server/io-github-ni-c-smtp-mcp"><img src="https://mcpindex.ai/api/v1/badge/io-github-ni-c-smtp-mcp" alt="mcpindex verdict" height="20" /></a>

Environment variables

SMTP_HOST

required

Hostname of the SMTP server, e.g. smtp.example.net.

SMTP_PORT

Port. Defaults to 587 for starttls, 465 for implicit, 25 for none.

SMTP_TLS

starttls (default), implicit or none. STARTTLS is required, never opportunistic.

SMTP_USER

required

Username for SMTP authentication.

SMTP_PASSWORD

requiredsecret

Password or app-specific password for SMTP authentication.

SMTP_FROM

required

The only sender this server will use, e.g. "Name <person@example.net>". There is no from parameter.

SMTP_REPLY_TO

Reply-To header on every message, e.g. "Team <team@example.net>". Unset means no Reply-To header and replies go to SMTP_FROM. There is no reply_to parameter.

SMTP_ALLOW_SEND

Set to "true" to register the sending tools. Defaults to false: the server cannot send until it is set.

SMTP_ALLOWED_RECIPIENTS

Comma-separated addresses and @domains this server may write to. Required with SMTP_ALLOW_SEND=true; "*" allows any.

SMTP_MAX_RECIPIENTS

Maximum distinct recipients across To, Cc and Bcc in one message. Default 10.

SMTP_MAX_SENDS_PER_HOUR

Sliding hourly cap on messages sent. Default 20.

SMTP_MAX_MESSAGE_BYTES

Maximum size of the composed message. Default 10485760.

SMTP_MAX_ATTACHMENT_BYTES

Maximum size of a single attachment. Default 5242880.

SMTP_ATTACHMENT_DIR

Directory attachments are read from. Unset means attachments are unavailable.

SMTP_ATTACHMENT_TYPES

Comma-separated content types that may be attached. Defaults to a document and image allowlist.

SMTP_SIGNATURE

Text appended below the standard signature delimiter of every message.

SMTP_AUDIT_LOG

File the audit lines are appended to, in addition to stderr.

SMTP_ALLOW_TOOLS

Comma-separated tool names, a prefix with one trailing *, or "essential" for the curated preset.

SMTP_DENY_TOOLS

Comma-separated tool names or prefixes to remove, applied after SMTP_ALLOW_TOOLS.

SMTP_INSECURE_TLS

Set to "true" to accept self-signed certificates. Prefer a proper internal CA.

SMTP_HOST

required

Hostname of the SMTP server, e.g. smtp.example.net.

SMTP_PORT

Port. Defaults to 587 for starttls, 465 for implicit, 25 for none.

SMTP_TLS

starttls (default), implicit or none. STARTTLS is required, never opportunistic.

SMTP_USER

required

Username for SMTP authentication.

SMTP_PASSWORD

requiredsecret

Password or app-specific password for SMTP authentication.

SMTP_FROM

required

The only sender this server will use, e.g. "Name <person@example.net>". There is no from parameter.

SMTP_REPLY_TO

Reply-To header on every message, e.g. "Team <team@example.net>". Unset means no Reply-To header and replies go to SMTP_FROM. There is no reply_to parameter.

SMTP_ALLOW_SEND

Set to "true" to register the sending tools. Defaults to false: the server cannot send until it is set.

SMTP_ALLOWED_RECIPIENTS

Comma-separated addresses and @domains this server may write to. Required with SMTP_ALLOW_SEND=true; "*" allows any.

SMTP_MAX_RECIPIENTS

Maximum distinct recipients across To, Cc and Bcc in one message. Default 10.

SMTP_MAX_SENDS_PER_HOUR

Sliding hourly cap on messages sent. Default 20.

SMTP_MAX_MESSAGE_BYTES

Maximum size of the composed message. Default 10485760.

SMTP_MAX_ATTACHMENT_BYTES

Maximum size of a single attachment. Default 5242880.

SMTP_ATTACHMENT_DIR

Directory attachments are read from. Unset means attachments are unavailable.

SMTP_ATTACHMENT_TYPES

Comma-separated content types that may be attached. Defaults to a document and image allowlist.

SMTP_SIGNATURE

Text appended below the standard signature delimiter of every message.

SMTP_AUDIT_LOG

File the audit lines are appended to, in addition to stderr.

SMTP_ALLOW_TOOLS

Comma-separated tool names, a prefix with one trailing *, or "essential" for the curated preset.

SMTP_DENY_TOOLS

Comma-separated tool names or prefixes to remove, applied after SMTP_ALLOW_TOOLS.

SMTP_INSECURE_TLS

Set to "true" to accept self-signed certificates. Prefer a proper internal CA.

MCP quality score · maturity, not trust · methodology

freshness

completeness

installability

documentation

stability

Alternatives in Email

BlitzAPI

ai.blitz-api/b2b-data

Search and enrich B2B companies and people: verified work emails, US phone numbers, job postings.

Oneprofile

ai.getoneprofile/oneprofile

Find prospects, research them, and run email and LinkedIn outreach in your Oneprofile workspace.

Terlido

io.github.nichovski/terlido

Cold email: campaigns, leads, mailboxes, warmup and inbox replies.

Install this server

Claude Desktop (claude_desktop_config.json)

{
  "mcpServers": {
    "smtp-mcp": {
      "command": "npx",
      "args": [
        "-y",
        "--",
        "@ni-c/smtp-mcp"
      ],
      "env": {
        "SMTP_HOST": "<smtp_host>",
        "SMTP_PORT": "<smtp_port>",
        "SMTP_TLS": "<smtp_tls>",
        "SMTP_USER": "<smtp_user>",
        "SMTP_PASSWORD": "<your-smtp_password>",
        "SMTP_FROM": "<smtp_from>",
        "SMTP_REPLY_TO": "<smtp_reply_to>",
        "SMTP_ALLOW_SEND": "<smtp_allow_send>",
        "SMTP_ALLOWED_RECIPIENTS": "<smtp_allowed_recipients>",
        "SMTP_MAX_RECIPIENTS": "<smtp_max_recipients>",
        "SMTP_MAX_SENDS_PER_HOUR": "<smtp_max_sends_per_hour>",
        "SMTP_MAX_MESSAGE_BYTES": "<smtp_max_message_bytes>",
        "SMTP_MAX_ATTACHMENT_BYTES": "<smtp_max_attachment_bytes>",
        "SMTP_ATTACHMENT_DIR": "<smtp_attachment_dir>",
        "SMTP_ATTACHMENT_TYPES": "<smtp_attachment_types>",
        "SMTP_SIGNATURE": "<smtp_signature>",
        "SMTP_AUDIT_LOG": "<smtp_audit_log>",
        "SMTP_ALLOW_TOOLS": "<smtp_allow_tools>",
        "SMTP_DENY_TOOLS": "<smtp_deny_tools>",
        "SMTP_INSECURE_TLS": "<smtp_insecure_tls>"
      }
    }
  }
}

Cursor (.cursor/mcp.json)

{
  "mcpServers": {
    "smtp-mcp": {
      "command": "npx",
      "args": [
        "-y",
        "--",
        "@ni-c/smtp-mcp"
      ],
      "env": {
        "SMTP_HOST": "<smtp_host>",
        "SMTP_PORT": "<smtp_port>",
        "SMTP_TLS": "<smtp_tls>",
        "SMTP_USER": "<smtp_user>",
        "SMTP_PASSWORD": "<your-smtp_password>",
        "SMTP_FROM": "<smtp_from>",
        "SMTP_REPLY_TO": "<smtp_reply_to>",
        "SMTP_ALLOW_SEND": "<smtp_allow_send>",
        "SMTP_ALLOWED_RECIPIENTS": "<smtp_allowed_recipients>",
        "SMTP_MAX_RECIPIENTS": "<smtp_max_recipients>",
        "SMTP_MAX_SENDS_PER_HOUR": "<smtp_max_sends_per_hour>",
        "SMTP_MAX_MESSAGE_BYTES": "<smtp_max_message_bytes>",
        "SMTP_MAX_ATTACHMENT_BYTES": "<smtp_max_attachment_bytes>",
        "SMTP_ATTACHMENT_DIR": "<smtp_attachment_dir>",
        "SMTP_ATTACHMENT_TYPES": "<smtp_attachment_types>",
        "SMTP_SIGNATURE": "<smtp_signature>",
        "SMTP_AUDIT_LOG": "<smtp_audit_log>",
        "SMTP_ALLOW_TOOLS": "<smtp_allow_tools>",
        "SMTP_DENY_TOOLS": "<smtp_deny_tools>",
        "SMTP_INSECURE_TLS": "<smtp_insecure_tls>"
      }
    }
  }
}

Cline (cline_mcp_settings.json)

npx -y -- @ni-c/smtp-mcp

Claude Code (claude mcp add)

claude mcp add --scope user smtp-mcp -- npx -y -- @ni-c/smtp-mcp

Gemini CLI (gemini mcp add)

gemini mcp add -s user smtp-mcp npx -y -- @ni-c/smtp-mcp

Claude Desktop (Docker)

{
  "mcpServers": {
    "smtp-mcp": {
      "command": "docker",
      "args": [
        "run",
        "--rm",
        "-i",
        "--",
        "ghcr.io/ni-c/smtp-mcp:0.2.0"
      ],
      "env": {
        "SMTP_HOST": "<smtp_host>",
        "SMTP_PORT": "<smtp_port>",
        "SMTP_TLS": "<smtp_tls>",
        "SMTP_USER": "<smtp_user>",
        "SMTP_PASSWORD": "<your-smtp_password>",
        "SMTP_FROM": "<smtp_from>",
        "SMTP_REPLY_TO": "<smtp_reply_to>",
        "SMTP_ALLOW_SEND": "<smtp_allow_send>",
        "SMTP_ALLOWED_RECIPIENTS": "<smtp_allowed_recipients>",
        "SMTP_MAX_RECIPIENTS": "<smtp_max_recipients>",
        "SMTP_MAX_SENDS_PER_HOUR": "<smtp_max_sends_per_hour>",
        "SMTP_MAX_MESSAGE_BYTES": "<smtp_max_message_bytes>",
        "SMTP_MAX_ATTACHMENT_BYTES": "<smtp_max_attachment_bytes>",
        "SMTP_ATTACHMENT_DIR": "<smtp_attachment_dir>",
        "SMTP_ATTACHMENT_TYPES": "<smtp_attachment_types>",
        "SMTP_SIGNATURE": "<smtp_signature>",
        "SMTP_AUDIT_LOG": "<smtp_audit_log>",
        "SMTP_ALLOW_TOOLS": "<smtp_allow_tools>",
        "SMTP_DENY_TOOLS": "<smtp_deny_tools>",
        "SMTP_INSECURE_TLS": "<smtp_insecure_tls>"
      }
    }
  }
}

Verdict API

curl -s mcpindex.ai/api/v1/trust/server/io-github-ni-c-smtp-mcp

Free-tier verdict as JSON: decision + dimensions + severity. Call it from your agent before it invokes a tool it just discovered.

Details

version: v0.2.0
category: Email
verdict expires: 2026-10-26
quality: 89 / 100
operator: ni-c

Listing

Listed from the official MCP registry. Unclaimed by its maintainer. Maintainer? Email us →

Provenance

Each verdict is bound to a hash of the exact description it judged, so a re-crawl that changes the text produces a new record rather than silently inheriting this one. Verdict history is hash-chained and anchored to Bitcoin via OpenTimestamps (latest confirmed at block 972,115). Verify it yourself.

Links

Repository →Website →