MailCatcher

What MailCatcher is

MailCatcher is a free, open-source tool for inspecting application email during development. It runs a local SMTP server, captures messages, and displays them in a web interface, where developers can review mail sent to a local endpoint. Captured messages can be viewed as HTML, plain text, or source when available. For HTML messages, MailCatcher adjusts the content so embedded images display and links open in a new window. It lists attachments, supports downloading individual message parts, and can provide the original email. New messages appear instantly in browsers with WebSockets support; otherwise, the interface refreshes every thirty seconds. The URL API provides message lists and metadata in JSON, along with message HTML, plain text, attachments, and full source. The maker documents setup examples for Rails, PHP, and Django, plus installation as a Ruby gem or via a Docker image. MailCatcher requires Ruby 3.3 or newer, and dependencies may require build tools. The project uses the MIT License. Its mail processing is basic, and UTF-8 is not completely supported directly over the wire; the maker advises using a mail library that encodes according to SMTP server capabilities.

Who it suits

MailCatcher suits developers who want to capture and inspect application email at a local SMTP endpoint during development. It is available for self-hosted use and supports an API for message access.

Limits

Mail processing is basic, and UTF-8 sent directly over the wire is not completely supported. The maker advises using a mail library that encodes according to SMTP server capabilities.

Getting started

1. Open the MailCatcher website for installation instructions
2. Install MailCatcher as a Ruby gem or use the Docker image
3. Check that Ruby 3.3 or newer is available if using the Ruby installation
4. Configure the application to send mail to a local SMTP endpoint
5. Use the web interface or URL API to inspect captured messages

Verdict

MailCatcher provides a local way to inspect development email, with message views, attachment downloads, and API access. Check its Ruby requirement and UTF-8 limitation before relying on it for a workflow.