MailDev

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mcp-name: io.github.pierre3/maildev-mcp

An MCP (Model Context Protocol) server for MailDev.
Manage MailDev Docker containers and inspect received emails directly from your AI-powered editor or MCP client.

This server is intended for local development and test automation scenarios where an MCP client needs to:

• start or stop a MailDev container
• inspect inbox contents
• wait for emails after triggering application behavior
• inspect HTML bodies and attachments
• verify attachment integrity byte-for-byte

Installation

Install as a global .NET tool:

dotnet tool install -g MailDevMcp

After installation, the maildev-mcp command becomes available.

MCP Client Configuration

Add the following to your MCP client settings (e.g. Claude Desktop, VS Code, etc.):

{
  "mcpServers": {
    "maildev-mcp": {
      "command": "maildev-mcp",
      "env": {
        "MAILDEV_API_PORT": "1080"
      }
    }
  }
}

Environment Variables

Variable	Default	Description
MAILDEV_API_PORT	1080	Port number for the MailDev REST API

Typical Workflow

1. Call StartMaildev to launch a local MailDev container
2. Trigger your application to send an email
3. Call WaitForEmail if delivery is asynchronous
4. Use ListEmails, SearchEmails, or GetEmail to inspect the result
5. Use GetEmailHtml, GetAttachmentContent, or VerifyAttachment when deeper validation is needed
6. Clean up with DeleteEmail, DeleteAllEmails, or StopMaildev

Available Tools

Tool	Description
StartMaildev	Start the MailDev Docker container with configurable SMTP port, API port, authentication, and TLS
StopMaildev	Stop and remove the MailDev Docker container
MaildevStatus	Check the running status of MailDev
ListEmails	Retrieve the list of received emails
GetEmail	Get the details of an email by ID, including attachment information
GetEmailHtml	Get the HTML body of an email by ID
SearchEmails	Search received emails by subject, sender, or recipient
DeleteEmail	Delete a single email by ID
DeleteAllEmails	Delete all received emails
WaitForEmail	Wait until a new email matching given criteria arrives (useful for test automation)
GetAttachmentContent	Get the raw Base64-encoded content of an email attachment
VerifyAttachment	Verify that an email attachment matches the original data by byte-by-byte comparison

Tool Behavior Notes

• StartMaildev
  • Supports custom SMTP and API ports
  • Supports optional SMTP authentication
  • Treats empty or whitespace-only credentials as authentication disabled
  • Supports TLS with a generated self-signed certificate
• GetEmail and ListEmails
  • Render missing or empty subjects as (no subject)
  • Render missing address lists as (none)
• WaitForEmail
  • Polls MailDev until a matching email arrives or the timeout is reached
  • Reports transient MailDev connection failures in the returned message when they occur during polling
• VerifyAttachment
  • Accepts a Base64-encoded original payload
  • Compares the received attachment byte-by-byte
  • Reports either exact match, size mismatch, or content mismatch

Requirements and Assumptions

• Docker must be installed and available on the same machine where this MCP server runs
• MailDev is accessed through its HTTP API on localhost
• The configured API port in the MCP client must match the MailDev API port exposed by Docker

Prerequisites

• .NET 10 SDK or later
• Docker (for running the MailDev container)

Building from Source

git clone https://github.com/pierre3/MailDevMcp.git
cd MailDevMcp
dotnet pack -c Release
dotnet tool install -g --add-source ./bin/Release MailDevMcp

License

MIT