- Home
- Email Testing Software
- MailDev
MailDev
What it is
MailDev is a free, local SMTP server and web inbox for developers checking email generated by their applications during development. It listens for SMTP mail on port 1025 and shows rendered HTML, plain text, headers, and raw source. Its responsive preview helps inspect rendering at different viewport widths. A REST API under `/api` supports listing, reading, searching, downloading, and deleting messages, while WebSockets add new messages without refreshing or polling. MailDev documents connections from Nodemailer, Django, Ruby on Rails, Laravel, Spring Boot, and any language that speaks SMTP. An optional MCP server lets compatible AI clients search and read the development inbox and check delivery. Installation options include npx, a global npm package, and Docker. Selected messages can be relayed through an outgoing SMTP server with optional auto-relay rules. It runs locally and is free and MIT licensed. The default setup has no authentication, accepts mail from anyone, and stores messages unencrypted.
For and against
For
- Free and open source under MIT
- Displays HTML, text, headers, and raw source
- REST API manages inbox messages
- Live WebSocket inbox updates
- Optional SMTP relay rules
Against
- No authentication by default
- Stores email unencrypted
- Not intended for public or production use
- Email retention is unlimited by default
The verdict
MailDev combines a local inbox, SMTP listener, API, and rendering preview for development email checks. Its permissive default security settings require keeping it away from public or production traffic.
Who it suits
It suits developers testing application-generated email in local or development environments. Teams using SMTP-capable languages or the listed frameworks can connect it to their projects.
Plans and prices
MailDev
Free and open source · MIT licensed · Runs locally
Read 5 Oct 2026 · maildev.github.io
On the record
- AI integration
- MailDev includes an optional MCP server that lets compatible AI clients search and read the development inbox and check email delivery.maildev.github.io · read 5 Oct 2026
- Audience
- The maker describes MailDev as a development tool for developers testing email generated by their projects.github.com · read 5 Oct 2026
- Email formats
- The inbox displays rendered HTML, plain text, headers, and raw email source.maildev.github.io · read 5 Oct 2026
- Email retention
- MailDev keeps emails without a configured limit by default; its `--max-emails` option can cap the inbox and discard older messages.github.com · read 5 Oct 2026
- Framework integrations
- The docs provide setup examples for Nodemailer, Django, Ruby on Rails, Laravel, and Spring Boot, and say any language that speaks SMTP can connect.maildev.github.io · read 5 Oct 2026
- Install options
- The maker documents running MailDev with npx, a global npm install, or Docker.maildev.github.io · read 5 Oct 2026
- Live updates
- New messages appear in the inbox over WebSockets without a refresh or polling.maildev.github.io · read 5 Oct 2026
- Preview
- The web interface offers a responsive preview for checking how email renders at different viewport widths.maildev.github.io · read 5 Oct 2026
- Purpose
- MailDev is a local SMTP server and web inbox for developers to catch and inspect email sent by an app during development.maildev.github.io · read 5 Oct 2026
- Relay
- MailDev can selectively relay messages through a configured outgoing SMTP server, with optional auto-relay rules.github.com · read 5 Oct 2026
- Security
- MailDev accepts mail from anyone, stores it unencrypted, and has no authentication by default, so the docs warn against exposing it to the public internet or using it for production traffic.maildev.github.io · read 5 Oct 2026
- SMTP and API
- MailDev listens for SMTP on port 1025 and provides a REST API under `/api` for listing, reading, searching, downloading, and deleting mail.maildev.github.io · read 5 Oct 2026
