Add instructions on setting up email server

docs/setup.rst

@@ -130,6 +130,32 @@ to create new data source connection.
 See :doc:`documentation </datasources>` for the different options.
 Your instance comes ready with dependencies needed to setup supported sources.
 
+Mail Configuration
+------------------
+
+For the system to be able to send emails (for example when alerts trigger), you need to set the mail server to use and the
+host name of your re:dash server. If you're using one of our images, you can do this by editing the `.env` file:
+
+.. code::
+
+   # Note that not all values are required, as they have default values.
+
+   export MAIL_SERVER = "" # default: localhost
+   export MAIL_PORT = "" # default: 25
+   export MAIL_USE_TLS = "" # default: False
+   export MAIL_USE_SSL = "" # default: False
+   export MAIL_USERNAME = "" # default: None
+   export MAIL_PASSWORD = "" # default: None
+   export MAIL_DEFAULT_SENDER = "" # Email address to send from
+
+   export HOST = "" # base address of your re:dash instance, for example: "https://demo.redash.io"
+
+- Note that not all values are required, as there are default values.
+- It's recommended to use some mail service, like `Amazon SES <https://aws.amazon.com/ses/>`__, `Mailgun <http://www.mailgun.com/>`__
+  or `Mandrill <http://mandrillapp.com>`__ to send emails to ensure deliverability.
+
+To test email configuration, you can run `bin/run ./manage.py send_test_mail` (from `/opt/redash/current`).
+
 How to upgrade?
 ---------------