[ADD] email marketing: essentials, mailing lists, unsubscriptions

Author: samueljlieber

content/applications/marketing.rst

@@ -7,6 +7,7 @@ Marketing
 
 .. toctree::
 
+   marketing/email_marketing
    marketing/marketing_automation
    marketing/sms_marketing
    marketing/events

content/applications/marketing/email_marketing.rst

@@ -0,0 +1,10 @@
+:nosearch:
+
+===============
+Email Marketing
+===============
+
+.. toctree::
+   :titlesonly:
+
+   email_marketing/overview

content/applications/marketing/email_marketing/overview.rst

@@ -0,0 +1,12 @@
+:nosearch:
+
+========
+Overview
+========
+
+.. toctree::
+   :titlesonly:
+
+   overview/email_marketing_essentials
+   overview/mailing_lists
+   overview/manage_unsubscriptions