While developing applications, sometimes I want to test email output. To make sure the whole process is as it should be in production, I made a smal mailserver that can be embedded to a development environment for testing mail output.
Below you'll find the documentation of the MailCatcher.
When you're working as a developer or tester on an application that sends out emails, you want to prevent that mails end up in production environments, or worse, at actual clients.
So when you are testing an email functionality inside an application, this container can be of use to catch the mail so you can see what's supposed to be sent out.
To use this container, simply add the following service to your docker-compose.yaml:
services: mailcatcher: image: garrcomm/mailcatcher ports: - "127.0.0.1:25:25" - "127.0.0.1:465:465" - "127.0.0.1:80:80"
All mails delivered to this container at port 25 (SMTP) or 465 (SSMTP) will be available through the webinterface at port 80 (HTTP).
If you're application is also in the same Docker Compose project, you can deliver its mails to
mailcatcher:25 and port 25 doesn't need to be exposed outside of the project network.
You can even go a bit further in the service declaration in your docker-compose.yaml file. This example shows some varieties:
services: mailcatcher: image: garrcomm/mailcatcher volumes: - ./examples/mails:/var/smtpserver:cached environment: BASE_HREF: /mailcatcher/ ports: - "127.0.0.1:25:25" - "127.0.0.1:465:465" - "127.0.0.1:80:80"
./examples/mailsin the host OS will contain the .eml files. This can be useful to get easy access to the email files.
/. A use case can be if you're using a traefik, nginx or other proxy container that changes the URL.
A lot of applications, mostly Unix based, use sendmail to deliver mails. This package provides a drop-in replacement that delivers mail to an SMTP server instead.
In, for example, PHP, you can configure this by adding this in the
sendmail_path = "/absolute/path/to/mcsendmail.sh -t -i"
When the server name or port number is different, try;
sendmail_path = "/absolute/path/to/mcsendmail.sh -t -i -Shostname:portnumber"
It's also possible to set the environment values
SMTP_PORT instead of using the
All available command line arguments of mcsendmail.sh explained:
-f[mail-address] Sets the name of the 'from' person (i.e., the envelope sender of the mail). -V[envelope-id] Set the original envelope id. -S[host:port] Defines the SMTP host and port to connect to. -t Read message for recipients. The Bcc: line will be deleted before transmission. -i Ignore dots alone on lines by themselves in incoming messages. -r[mail-address] An alternate and obsolete form of the -f flag.
In the root is a
docker-compose.yaml which is made for development purposes.
When bringing up the environment by
docker compose up -d it's possible to run this locally.
To send an email, execute one of the examples, or execute them all by running bin/run-all-examples.sh or bin/run-all-examples.bat. The result should end up in the examples/mails folder and in the web interface. To go to the web interface, open http://localhost/.
Most files are available immediately after a change, but if a config file is changed, it's possible you need to restart the container by
docker compose restart mailcatcher.
If you modify the Dockerfile you also need to rebuild the container by
docker compose build mailcatcher.
To fetch all dependencies for the web application, execute: