Chore: Moved the email ingress method to an env variable (#777) (#806)

* Chore: Moved the email ingress method to an env variable (#777)
* Moved the email ingress method in config to an environment variable
* Updated documentation to reflect this

* Added ingress config to staging env config (#777)
* Re-arranged the order in env configs so that email related configs are together

config/environments/development.rb

@@ -1,9 +1,6 @@
 Rails.application.configure do
   # Settings specified here will take precedence over those in config/application.rb.
 
-  # set this to appropriate ingress channel when you are doing development in local with regards to incoming emails
-  # config.action_mailbox.ingress = :sendgrid
-
   # In the development environment your application's code is reloaded on
   # every request. This slows down response time but is perfect for development
   # since you don't have to restart the web server when you make code changes.
@@ -64,6 +61,14 @@ Rails.application.configure do
 
   config.action_mailer.smtp_settings = smtp_settings
 
+  # Set this to appropriate ingress service for which the options are :
+  # :relay for Exim, Postfix, Qmail
+  # :mailgun for Mailgun
+  # :mandrill for Mandrill
+  # :postmark for Postmark
+  # :sendgrid for Sendgrid
+  config.action_mailbox.ingress = ENV.fetch('RAILS_INBOUND_EMAIL_SERVICE', 'relay').to_sym
+
   Rails.application.routes.default_url_options = { host: 'localhost', port: 3000 }
 
   # Print deprecation notices to the Rails logger.