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Catches mail and serves it through a dream.

MailCatcher runs a super simple SMTP server which catches any message sent to it to display in a web interface. Run mailcatcher, set your favourite app to deliver to smtp:// instead of your default SMTP server, then check out to see the mail that's arrived so far.

MailCatcher screenshot


  • Catches all mail and stores it for display.
  • Shows HTML, Plain Text and Source version of messages, as applicable.
  • Rewrites HTML enabling display of embedded, inline images/etc and opens links in a new window.
  • Lists attachments and allows separate downloading of parts.
  • Download original email to view in your native mail client(s).
  • Command line options to override the default SMTP/HTTP IP and port settings.
  • Mail appears instantly if your browser supports WebSockets, otherwise updates every thirty seconds.
  • Runs as a daemon in the background, optionally in foreground.
  • Sendmail-analogue command, catchmail, makes using mailcatcher from PHP a lot easier.
  • Keyboard navigation between messages


  1. gem install mailcatcher
  2. mailcatcher
  3. Go to
  4. Send mail through smtp://

Command Line Options

Use mailcatcher --help to see the command line options.

Usage: mailcatcher [options]

MailCatcher v0.8.0

        --ip IP                      Set the ip address of both servers
        --smtp-ip IP                 Set the ip address of the smtp server
        --smtp-port PORT             Set the port of the smtp server
        --http-ip IP                 Set the ip address of the http server
        --http-port PORT             Set the port address of the http server
        --messages-limit COUNT       Only keep up to COUNT most recent messages
        --http-path PATH             Add a prefix to all HTTP paths
        --no-quit                    Don't allow quitting the process
    -f, --foreground                 Run in the foreground
    -b, --browse                     Open web browser
    -v, --verbose                    Be more verbose
    -h, --help                       Display this help information
        --version                    Display the current version


Upgrading works the same as installation:

gem install mailcatcher


If you have trouble with the setup commands, make sure you have Ruby installed:

ruby -v
gem environment

You might need to install build tools for some of the gem dependencies. On Debian or Ubuntu, apt install build-essential. On macOS, xcode-select --install.

If you encounter issues installing thin, try:

gem install thin -v 1.5.1 -- --with-cflags="-Wno-error=implicit-function-declaration"


Please don't put mailcatcher into your Gemfile. It will conflict with your application's gems at some point.

Instead, pop a note in your README stating you use mailcatcher, and to run gem install mailcatcher then mailcatcher to get started.


Under RVM your mailcatcher command may only be available under the ruby you install mailcatcher into. To prevent this, and to prevent gem conflicts, install mailcatcher into a dedicated gemset with a wrapper script:

rvm default@mailcatcher --create do gem install mailcatcher
ln -s "$(rvm default@mailcatcher do rvm wrapper show mailcatcher)" "$rvm_bin_path/"


To set up your rails app, I recommend adding this to your environments/development.rb:

config.action_mailer.delivery_method = :smtp
config.action_mailer.smtp_settings = { :address => '', :port => 1025 }
config.action_mailer.raise_delivery_errors = false


For projects using PHP, or PHP frameworks and application platforms like Drupal, you can set PHP's mail configuration in your php.ini to send via MailCatcher with:

sendmail_path = /usr/bin/env catchmail -f some@from.address

You can do this in your Apache configuration like so:

php_admin_value sendmail_path "/usr/bin/env catchmail -f some@from.address"

If you've installed via RVM this probably won't work unless you've manually added your RVM bin paths to your system environment's PATH. In that case, run which catchmail and put that path into the sendmail_path directive above instead of /usr/bin/env catchmail.

If starting mailcatcher on alternative SMTP IP and/or port with parameters like --smtp-ip --smtp-port 10025, add the same parameters to your catchmail command:

sendmail_path = /usr/bin/env catchmail --smtp-ip --smtp-port 10025 -f some@from.address


For use in Django, add the following configuration to your projects'

    EMAIL_HOST = ''
    EMAIL_PORT = 1025
    EMAIL_USE_TLS = False


There is a Docker image available on Docker Hub:

$ docker run -p 1080 -p 1025 sj26/mailcatcher
Unable to find image 'sj26/mailcatcher:latest' locally
latest: Pulling from sj26/mailcatcher
8c6d1654570f: Already exists
f5649d186f41: Already exists
b850834ea1df: Already exists
d6ac1a07fd46: Pull complete
b609298bc3c9: Pull complete
ab05825ece51: Pull complete
Digest: sha256:b17c45de08a0a82b012d90d4bd048620952c475f5655c61eef373318de6c0855
Status: Downloaded newer image for sj26/mailcatcher:latest
Starting MailCatcher v0.9.0
==> smtp://

How those ports appear and can be accessed may vary based on your Docker configuration. For example, your may need to use etc instead of the listed address. But MailCatcher will run and listen to those ports on all IPs it can from within the Docker container.


A fairly RESTful URL schema means you can download a list of messages in JSON from /messages, each message's metadata with /messages/:id.json, and then the pertinent parts with /messages/:id.html and /messages/:id.plain for the default HTML and plain text version, /messages/:id/parts/:cid for individual attachments by CID, or the whole message with /messages/:id.source.


  • Mail processing is fairly basic but easily modified. If something doesn't work for you, fork and fix it or file an issue and let me know. Include the whole message you're having problems with.
  • Encodings are difficult. MailCatcher does not completely support utf-8 straight over the wire, you must use a mail library which encodes things properly based on SMTP server capabilities.


MailCatcher is just a mishmash of other people's hard work. Thank you so much to the people who have built the wonderful guts on which this project relies.


I work on MailCatcher mostly in my own spare time. If you've found Mailcatcher useful and would like to help feed me and fund continued development and new features, please donate via PayPal. If you'd like a specific feature added to MailCatcher and are willing to pay for it, please email me.


Copyright © 2010-2019 Samuel Cochran ( Released under the MIT License, see LICENSE for details.