Add Sendgrid integration (incoming email handling)

docs/mailgun.markdown

@@ -6,34 +6,7 @@ You can use the service [Mailgun](http://www.mailgun.com/) to create tasks direc
 This integration works with the inbound email service of Mailgun (routes).
 Kanboard use a webhook to handle incoming emails.
 
-Incoming emails workflow
-------------------------
-
-1. You send an email to a specific address, by example **something+myproject@inbound.mydomain.tld**
-2. Your email is forwarded to Mailgun SMTP servers
-3. Mailgun call the Kanboard webhook with the email in JSON format
-4. Kanboard parse the received email and create the task to the right project
-
-Note: New tasks are automatically created in the first column.
-
-Email format
-------------
-
-- The local part of the email address must use the plus separator, by example **kanboard+project123**
-- The string defined after the plus sign must match a project identifier, by example **project123** is the identifier of the project **Project 123**
-- The email subject becomes the task title
-- The email body becomes the task description (Markdown format)
-
-Incoming emails can be written in text or HTML formats.
-**Kanboard is able to convert simple HTML emails to Markdown**.
-
-Security and requirements
--------------------------
-
-- The Kanboard webhook is protected by a random token
-- The sender email address must match a Kanboard user
-- The Kanboard project must have a unique identifier, by example **MYPROJECT**
-- The Kanboard user must be member of the project
+The [incoming email workflow is described here](http://kanboard.net/documentation/email-tasks).
 
 Mailgun configuration
 ---------------------
@@ -53,9 +26,3 @@ Kanboard configuration
 1. Be sure that your users have an email address in their profiles
 2. Assign a project identifier to the desired projects: **Project settings > Edit**
 3. Try to send an email to your project
-
-Troubleshootings
-----------------
-
-- Test if your route match in the console
-- Double-check requirements mentioned above