btafoya/mailsandbox
If you are the rightful owner of mailsandbox and would like to certify it and/or have it hosted online, please leave a comment on the right or send an email to henry@mcphub.com.
MailSandbox is a versatile email testing and simulation tool designed for developers, offering a range of features including Postmark API emulation and an MCP server for AI-assisted debugging.
MailSandbox โ email testing & simulation for developers
Fork of Mailpit adding Postmark API emulation and an MCP server for AI-assisted debugging.
Inspired by and grateful to the original work on Mailpit and MailHog. See Credits.
Repository โข Installation โข Usage โข Postmark API โข MCP Server
MailSandbox is a small, fast, low-memory, zero-dependency, multi-platform email testing tool & API for developers.
It provides an SMTP server, modern web interface, REST API, Postmark API emulation, and an MCP server for AI-powered workflows.
Features
- ๐ Lightweight โ single static binary or multi-arch Docker image
- ๐ Modern Web UI โ view HTML, source, headers, attachments, search & filter
- ๐ฌ SMTP & POP3 servers โ STARTTLS/SSL/TLS, authentication, forwarding, relaying
- ๐ Testing tools โ HTML check, link check, spam score, screenshots, mobile preview
- ๐ท Tagging & filtering โ manual or automated (incl. plus addressing)
- โก Performance โ 100โ200 emails/sec, automatic pruning (default 500 emails)
- ๐งช Chaos mode โ inject SMTP errors to test resilience
- ๐ Integrations โ webhooks, browser notifications,
List-Unsubscribe
validation - ๐ Postmark API emulation โ drop-in replacement for Postmark during development
- ๐ค MCP server โ AI assistants (e.g., Claude Code) can list, search, and analyze messages
Installation
The web UI runs on http://0.0.0.0:8025
and SMTP on 0.0.0.0:1025
.
Script (Linux & macOS)
sudo sh < <(curl -sL https://raw.githubusercontent.com/btafoya/mailsandbox/main/install.sh)
Static binary
Download from releases, rename to mailsandbox
, and add to $PATH
.
Docker
docker run -d --name mailsandbox -p 8025:8025 -p 1025:1025 btafoya/mailsandbox
Usage
List options:
mailsandbox -h
Postmark API Emulation
Enable Postmark API emulation:
mailsandbox --postmark-api --postmark-token "your-secret-token"
Environment variables:
export MP_POSTMARK_API=true
export MP_POSTMARK_TOKEN=your-secret-token
mailsandbox
Example: Node.js
const postmark = require("postmark");
const client = new postmark.ServerClient("your-secret-token");
client.apiUrl = "http://localhost:8025";
client.sendEmail({ From:"a@x.com", To:"b@y.com", Subject:"Test", TextBody:"Hello" });
Endpoints:
POST /email
POST /email/batch
POST /email/withTemplate
MCP Server for AI Assistants
Enable MCP server:
mailsandbox --mcp-server --mcp-transport stdio
Environment variables:
export MP_MCP_SERVER=true
export MP_MCP_TRANSPORT=stdio
Docker with MCP
docker build -t mailsandbox-with-mcp .
docker run -d --name mailsandbox -p 127.0.0.1:8025:8025 -p 1025:1025 -e MP_MCP_SERVER=true -e MP_MCP_TRANSPORT=stdio -e MP_POSTMARK_API=true -e MP_POSTMARK_TOKEN=dev-token-123 mailsandbox-with-mcp
MCP tools
list_messages
โ list/filter emailsget_message
โ retrieve full messagesearch_messages
โ advanced searchanalyze_message
โ HTML, links, spam scoring
Migration Guide
- Binary name renamed
mailsandbox
; create a symlink if you prefermailpit
. - Default ports unchanged: HTTP
8025
, SMTP1025
. - APIs: REST API unchanged; Postmark & MCP are opt-in.
- Docker: use forked image for MCP/Postmark features.
Credits & Acknowledgements
- Mailpit โ by Axel Lenferna de la Motte and contributors. Original project and active development.
- MailHog โ the original inspiration for mainer email testing tools.
- MailSandbox โ maintained by Brian Tafoya, adding Postmark API emulation and MCP server support.
License
MailSandbox inherits the upstream license from Mailpit. See LICENSE
for details.