Add mailing documentation.

docs/topics/index.rst

@@ -18,5 +18,6 @@ Introductions to all the key parts of **Mayan EDMS** you'll need to know:
    indexes
    smart_links
    tags
+   mailing
    file_storage
    screenshots

docs/topics/mailing.rst

@@ -0,0 +1,17 @@
+=================
+Mailing documents
+=================
+
+To be able to send documents via email from inside Mayan EDMS you need to add
+and configure the following configuration variables in your
+mayan/settings/local.py file::
+
+  EMAIL_HOST = 'smtp.gmail.com'  # Or similar
+  EMAIL_PORT = 587
+  EMAIL_HOST_USER = '<your smtp username>'
+  EMAIL_HOST_PASSWORD = '<your smtp password>'
+  EMAIL_USE_TLS = True
+
+"Mail is sent using the SMTP host and port specified in the EMAIL_HOST and EMAIL_PORT settings. The EMAIL_HOST_USER andEMAIL_HOST_PASSWORD settings, if set, are used to authenticate to the SMTP server, and the EMAIL_USE_TLS and EMAIL_USE_SSL settings control whether a secure connection is used."
+
+For more details consult Django's documentation on the topic: https://docs.djangoproject.com/en/1.8/ref/settings/#email-host