SHSelfHostIndex

MailCatcher vs smtp4dev

A side-by-side comparison of two self-hosted mail servers options — licensing, setup difficulty, resource needs, and what each one replaces.

Not the right match-up?
MA MailCatcher Catch-all SMTP server for inspecting test email VS SM smtp4dev Fake SMTP server for development email testing
FeatureMailCatchersmtp4dev
Deploy effortUnder-an-hour setupUnder-an-hour setup
Health score72 · Good85 · Excellent
CategoryMail ServersMail Servers
LicenseMITGPL-3.0
LanguageRubyC#
Setup difficultyEasyEasy
Min. RAM128 MB128 MB
Deploymentdocker, binary, sourcedocker, binary
GitHub stars★ 6,780★ 3,979
First released20102015
ReplacesMailtrapMailtrap

What are MailCatcher and smtp4dev?

MailCatcher

MailCatcher runs a simple SMTP server that catches any message sent to it and displays it in a web interface for developers. It is a development tool for inspecting outgoing email without delivering it.

  • Catch-all SMTP server
  • Web UI for inspecting mail
  • View HTML and plain text
  • Developer testing tool

smtp4dev

smtp4dev is a dummy SMTP server that catches messages sent by applications and shows them in a web interface. It lets developers test email functionality without sending real mail.

  • Catches outgoing email
  • Web inbox viewer
  • IMAP access
  • API for automation

Read the full smtp4dev guide →

MailCatcher vs smtp4dev: key differences

MailCatcher is written in Ruby, while smtp4dev is built with C#. Licensing differs — MIT for MailCatcher versus GPL-3.0 for smtp4dev. MailCatcher is the more established project (first released 2010), while smtp4dev arrived in 2015.

Why pick each one

Choose MailCatcher if…

  • Released under the MIT license
  • Easy to set up — beginner-friendly
  • First-class Docker support for quick deployment
  • Mature project with 6.8k GitHub stars
MailCatcher details

Choose smtp4dev if…

  • Easy local testing
  • Cross-platform

Watch out for

  • Not for real delivery
  • Development use only
smtp4dev details

Frequently asked questions

Is MailCatcher or smtp4dev better?

Neither is universally better. MailCatcher has the larger community; both share a easy setup difficulty, so the decision comes down to features and licensing.

Are MailCatcher and smtp4dev free and open-source?

Yes. MailCatcher is licensed under MIT and smtp4dev under GPL-3.0. Both can be self-hosted at no software cost.

Can I run MailCatcher and smtp4dev with Docker?

MailCatcher: yes. smtp4dev: yes.

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