SMTP MCP server

by ni-c·io.github.ni-c/smtp-mcp·v0.2.0

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

B83/100grade B

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Safety scan

B83/100

full report

Adoption

Growing

0 stars43 downloads/wk

Reviews

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If you have run it, two minutes of your experience saves the next person an afternoon.

SMTP tools (7, 2 write)

write = sends, deletes, buys or posts

Read from the package source without running it. The installed server may list more.

forward_mail
Forwards a message to new recipients. Put the original text in
get_server_info
Reports the SMTP endpoint, the fixed sender address, who this server
preview_mail
Builds exactly the message a send would build and returns its
reply_mailwrite action
Sends a reply that mail clients will thread under the original. Pass
send_mailwrite action
Sends a new message from the configured sender. Asks the user to
test_connection
Opens a connection to the SMTP server, negotiates TLS and
validate_recipients
Says which of the given addresses this server is allowed to write to,

Public scan report

scanner v0.1.10 · 2026-10-15 · same rubric, same numbers if you re-run it

no findings

Code scan45 source files scanned25/25
–Live reliabilityno gateway calls yet and no remote to proben/a
–Tool poisoningtools not inspected (local package is not executed); not countedn/a
Auth qualitystatic API keys via environment variables6/15
Maintenancelast push 2 days ago15/15
Maintainer identityregistry namespace matches repository owner; GitHub account older than a year8/10

Overall 83/100. Components that don't apply are left out of the denominator. Any critical finding is an F.Rubric Appeal a finding JSON

How SMTP compares

Against every graded Email MCP server, from our own scans and uptime checks. Updated after each scan run.

Safety score: 83/100; higher than 75% of 916 Email servers
Tools: 7; the typical Email server has 7
Tools that change things: 29%; typical: 25%. Fewer write tools means less an agent can break
Downloads a week: 43; more than 30% of 235 Email servers with a package

What its tools let an agent do: 5 read · 2 send or post

Install SMTP in Claude Code, Cursor or VS Code

Runs npx -y @ni-c/smtp-mcp on your machine. Read the scan report first; the gateway never runs local packages.

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

Add to Cursor

What the publisher says

From the SMTP repository's README, as published. We do not edit it. Read it on GitHub

smtp-mcp

A Model Context Protocol (MCP) server for SMTP, the protocol every mail server speaks to accept a message for delivery.

Lets MCP clients like Claude Code, Claude Desktop or Codex send, reply to and forward mail from one configured address — with a human approving every message.

Seven tools is the ceiling, not the floor: SMTPALLOWTOOLS=essential registers a curated five instead, and a model picks the right tool far more reliably from five than from seven — see choosing which tools load.

What makes it different

It sends mail. That is why it is a separate server. Its counterpart imap-mcp reads a mailbox and deliberately has no way to send anything — that absence is its entire security argument, because an agent that can reach private data and process attacker-controlled content is only exploitable once it also has a way out. This server is that way out, so it does not get to make the same claim. It earns its place by narrowing the channel instead, and by living in its own process with its own credentials.

It is off when you install it. SMTPALLOWSEND defaults to false. Until it is set the sending tools are not registered at all — absent from tools/list, not refused at call time.

Shortened. The full README is on GitHub.

Nothing above is checked by us. What we check is on the safety report.

SMTP: common questions

Is SMTP MCP server safe?: Mostly: it is graded B (83/100). Read the SMTP safety report
How do I install SMTP?: It runs on your machine. Copy the Claude Code, Cursor, VS Code or Claude Desktop config from the install section.
Does SMTP need an API key?: Yes. The registry entry asks for SMTP_PASSWORD.
Is SMTP maintained?: The last commit was 21 days ago (2026-10-14). The latest release is v0.2.0.
What can I use instead of SMTP?: Servers from other publishers that do the same job: Proton Mail (unofficial) MCP server, Agenticmail MCP server and Imap MCP server. Compare all SMTP alternatives.
How does SMTP compare with other Email MCP servers?: safety score 83/100 (higher than 75% of 916 Email servers); tools 7 (the typical Email server has 7); tools that change things 29% (typical: 25%. Fewer write tools means less an agent can break). Full comparison.

Alternatives to SMTP

Same job from other publishers: the closest match first, then the best rated.

All SMTP alternatives →

Proton Mail (unofficial)
Unofficial Proton Mail MCP — send, read, search & organize email over SMTP and IMAP
not reviewed
Growing
B
Agenticmail
Real email and SMS for AI agents — send mail, receive verification codes, drive a real inbox.
not reviewed
Established
B
Imap
IMAP/SMTP MCP server to search, read, organize, send, reply & forward email for AI assistants
not reviewed
Established
A
Openagentemail
Unlimited agent mailboxes — create identities, read/wait for mail, extract OTPs, send email.
not reviewed
Growing
B
Fluxmail
Read, search, draft, send, and organize email through Gmail, Outlook, and IMAP/SMTP mailboxes.
not reviewed
Growing
B

Run it through the gateway

Local package. It runs on your machine, not through the gateway.

Rating: —
Safety grade: B · 83/100
Stars: 0
Downloads/wk: 43
Price: Free
Licence: MIT
Transport: Local · mixed
Version: 0.2.0
Category: Email
Last release: 2026-10-14

Credentials it needs

SMTP_HOSTHostname of the SMTP server, e.g. smtp.example.net.
SMTP_PORTPort. Defaults to 587 for starttls, 465 for implicit, 25 for none.
SMTP_TLSstarttls (default), implicit or none. STARTTLS is required, never opportunistic.
SMTP_USERUsername for SMTP authentication.
SMTP_PASSWORDsecretPassword or app-specific password for SMTP authentication.
SMTP_FROMThe only sender this server will use, e.g. "Name <person@example.net>". There is no from parameter.
SMTP_REPLY_TOReply-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_SENDSet to "true" to register the sending tools. Defaults to false: the server cannot send until it is set.
SMTP_ALLOWED_RECIPIENTSComma-separated addresses and @domains this server may write to. Required with SMTP_ALLOW_SEND=true; "*" allows any.
SMTP_MAX_RECIPIENTSMaximum distinct recipients across To, Cc and Bcc in one message. Default 10.
SMTP_MAX_SENDS_PER_HOURSliding hourly cap on messages sent. Default 20.
SMTP_MAX_MESSAGE_BYTESMaximum size of the composed message. Default 10485760.
SMTP_MAX_ATTACHMENT_BYTESMaximum size of a single attachment. Default 5242880.
SMTP_ATTACHMENT_DIRDirectory attachments are read from. Unset means attachments are unavailable.
SMTP_ATTACHMENT_TYPESComma-separated content types that may be attached. Defaults to a document and image allowlist.
SMTP_SIGNATUREText appended below the standard signature delimiter of every message.
SMTP_AUDIT_LOGFile the audit lines are appended to, in addition to stderr.
SMTP_ALLOW_TOOLSComma-separated tool names, a prefix with one trailing *, or "essential" for the curated preset.
SMTP_DENY_TOOLSComma-separated tool names or prefixes to remove, applied after SMTP_ALLOW_TOOLS.
SMTP_INSECURE_TLSSet to "true" to accept self-signed certificates. Prefer a proper internal CA.
SMTP_HOSTHostname of the SMTP server, e.g. smtp.example.net.
SMTP_PORTPort. Defaults to 587 for starttls, 465 for implicit, 25 for none.
SMTP_TLSstarttls (default), implicit or none. STARTTLS is required, never opportunistic.
SMTP_USERUsername for SMTP authentication.
SMTP_PASSWORDsecretPassword or app-specific password for SMTP authentication.
SMTP_FROMThe only sender this server will use, e.g. "Name <person@example.net>". There is no from parameter.
SMTP_REPLY_TOReply-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_SENDSet to "true" to register the sending tools. Defaults to false: the server cannot send until it is set.
SMTP_ALLOWED_RECIPIENTSComma-separated addresses and @domains this server may write to. Required with SMTP_ALLOW_SEND=true; "*" allows any.
SMTP_MAX_RECIPIENTSMaximum distinct recipients across To, Cc and Bcc in one message. Default 10.
SMTP_MAX_SENDS_PER_HOURSliding hourly cap on messages sent. Default 20.
SMTP_MAX_MESSAGE_BYTESMaximum size of the composed message. Default 10485760.
SMTP_MAX_ATTACHMENT_BYTESMaximum size of a single attachment. Default 5242880.
SMTP_ATTACHMENT_DIRDirectory attachments are read from. Unset means attachments are unavailable.
SMTP_ATTACHMENT_TYPESComma-separated content types that may be attached. Defaults to a document and image allowlist.
SMTP_SIGNATUREText appended below the standard signature delimiter of every message.
SMTP_AUDIT_LOGFile the audit lines are appended to, in addition to stderr.
SMTP_ALLOW_TOOLSComma-separated tool names, a prefix with one trailing *, or "essential" for the curated preset.
SMTP_DENY_TOOLSComma-separated tool names or prefixes to remove, applied after SMTP_ALLOW_TOOLS.
SMTP_INSECURE_TLSSet to "true" to accept self-signed certificates. Prefer a proper internal CA.

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