This adds mailcatcher, which is accessible through your boot2docker ip on port 1080. To find out which IP your boot2docker is on, type boot2docker ip
in your terminal. Mailcatcher will be running on http://<boot2dockerIp>:1080
Add the following to your docker-compose.yml file:
mailcatcher:
image: yappabe/mailcatcher
ports:
- 1025:1025
- 1080:1080
Next, add this container to your php container's links.
You can now use mailcatcher as an smtp server, simply use 'mailcatcher', or whatever you named this container as host on port 1025.