MailDev

Free plan APISelf-hostedWeb

What MailDev is

MailDev is a local SMTP server and web inbox for developers who need to inspect email generated by an app during development. It shows messages as rendered HTML or plain text, alongside headers and raw source, and provides a responsive preview for checking how email appears at different viewport widths. Apps can send mail over SMTP on port 1025; the REST API under `/api` supports listing, reading, searching, downloading, and deleting messages. New mail appears through WebSockets without refreshing the inbox. MailDev can work with any language that speaks SMTP, and its documentation includes examples for Nodemailer, Django, Ruby on Rails, Laravel, and Spring Boot. An optional MCP server lets compatible AI clients search and read the development inbox and check delivery. You can run MailDev with npx, a global npm install, or Docker. It is free and open source under the MIT license. It accepts mail without authentication by default and stores it unencrypted, so it is intended for development, not public exposure or production traffic.

Who it suits

MailDev suits developers who want to inspect email their projects generate during development. Its SMTP and API access also fit teams connecting different languages or tools to a local inbox.

What it does well

Displays rendered HTML, plain text, headers, and raw source
REST API supports mail search and management
New messages appear over WebSockets
Can relay selected messages through an outgoing SMTP server
Free and open source under the MIT license

What to know first

No authentication by default
Stores messages unencrypted
Email retention is unlimited by default

Plans

Plan	Billed and limits	Price
MailDev	Free and open source · MIT licensed · Runs locally	Free

As maildev.github.io lists them, read 5 Oct 2026. The maker's own page has the final word.

Getting started

Open the MailDev website for the maker's documentation.
Choose an install route: npx, global npm install, or Docker.
Connect an app to SMTP on port 1025, using a documented framework example or another SMTP-capable language.
Open the web inbox to inspect messages and their rendered or raw content.

Verdict

MailDev brings message inspection, rendering previews, and mail management into a development inbox. Its default lack of authentication and unencrypted storage make it unsuitable for public exposure or production traffic.

Questions

Is MailDev free?

Yes. The MailDev plan is free, and it is open source under the MIT license.

Which platforms does MailDev support?

Its listed platforms are API, self-hosted, and web. The maker documents running it with npx, a global npm install, or Docker.

Can an application connect to MailDev?

Yes. MailDev listens for SMTP on port 1025, and any language that speaks SMTP can connect. It also provides a REST API under `/api`.

Can MailDev relay messages?

It can selectively relay messages through a configured outgoing SMTP server, with optional auto-relay rules.

Is MailDev suitable for production email?

The maker warns against production traffic and public exposure. By default, MailDev accepts mail from anyone, stores it unencrypted, and has no authentication.

Does MailDev limit how long emails are kept?

There is no configured retention limit by default. The `--max-emails` option can cap the inbox and discard older messages.

Facts from MailDev's own pages

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, 5 Oct 2026
Audience: The maker describes MailDev as a development tool for developers testing email generated by their projects. · github.com, 5 Oct 2026
Email formats: The inbox displays rendered HTML, plain text, headers, and raw email source. · maildev.github.io, 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, 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, 5 Oct 2026
Install options: The maker documents running MailDev with npx, a global npm install, or Docker. · maildev.github.io, 5 Oct 2026
Live updates: New messages appear in the inbox over WebSockets without a refresh or polling. · maildev.github.io, 5 Oct 2026
Preview: The web interface offers a responsive preview for checking how email renders at different viewport widths. · maildev.github.io, 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, 5 Oct 2026
Relay: MailDev can selectively relay messages through a configured outgoing SMTP server, with optional auto-relay rules. · github.com, 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, 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, 5 Oct 2026

Where MailDev stands on Freedom251

Email Testing Software#7 of 28