Letterkeel: Send Email via SMTP, Resend, SendGrid & Mailgun

dev.workers.cybermax-tools.cybermaxPublished by cybermax.cybermax-tools.workers.devv1.0.1Updated Oct 24, 2026

Letterkeel: send email from your own domain via SMTP, Resend, SendGrid, Mailgun, Postmark

VerifiedStreamable HTTPWeb executableCommunication & Collaboration

Overview

AI-generated overview

Lets an assistant send email from your own domain through SMTP, Resend, SendGrid, Mailgun or Postmark.

What you can do
Letterkeel is a remote MCP server that gives an assistant the ability to send email from your own domain. It supports several delivery backends: SMTP, Resend, SendGrid, Mailgun and Postmark. The manifest lists no individual tools, so the exact tool names and parameters are not documented here.
When to use it
Use it when you want an assistant to compose and send email from a domain you control, and you already have an account with one of the supported delivery providers. It is not aimed at reading inboxes or managing mailboxes.
Requirements
A remote endpoint reached over streamable HTTP with OAuth authentication. Requests carry an Authorization header holding an Apify API token as a Bearer credential. An Apify account and a configured email delivery provider (SMTP, Resend, SendGrid, Mailgun or Postmark) are needed.
Before you install
The Authorization header carries an Apify API token, a secret that should be kept private. Runs are billed per email recipient accepted to your Apify account, so sending can cost money. The server sends real email from your domain, which is hard to undo once delivered.

Installation

In SourceWeft

  1. Open Letterkeel: Send Email via SMTP, Resend, SendGrid & Mailgun in the dashboard and add it to a workspace.
  2. Connect the required credentials. They are stored privately and never shown on public pages.
  3. Enable the server for the chats that should use its tools.

Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.

Use with an agent

Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.

Read https://sourceweft.com/mcp/dev.workers.cybermax-tools.cybermax%2Fsend-email/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.

Read the install guide the agent follows

Other MCP clients

Add this to your client's mcpServers config. The client completes OAuth sign-in on first connect.

{
  "mcpServers": {
    "letterkeel-send-email-via-smtp-resend-se": {
      "type": "http",
      "url": "https://mcp.apify.com/?tools=cybermax/send-email&via=mcp-registry"
    }
  }
}

Tools

0
This server asks you to sign in, so SourceWeft could not read its tools without an account and has not indexed them. What a connected account sees can depend on that account and its permissions.

Version history

1
  1. v1.0.1LatestOct 10, 2026

Score

67% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

  • Reached in the last 30 daysRequired25 pts
  • Auth declaredRequired10 pts
  • Tools listed15 pts

    Answer tools/list without a credential, or ship a package that starts in a sandbox without one.

  • DescriptionRequired15 pts
  • Logo10 pts
  • Documentation15 pts

    Declare a GitHub repository with a README, or serve resource_documentation in the OAuth protected-resource metadata.

  • LicenseNot applicable

    A hosted service is used under its provider's terms, so no license is expected here. This check is left out of the percentage.