Add Sendgrid integration (incoming email handling)

docs/postmark.markdown

@@ -6,40 +6,15 @@ You can use the service [Postmark](https://postmarkapp.com/) to create tasks dir
 This integration works with the inbound email service of Postmark.
 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 Postmark SMTP servers
-3. Postmark 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 (From header) 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).
 
 Postmark configuration
 ----------------------
 
-- Follow the [official documentation about inbound email processing](http://developer.postmarkapp.com/developer-process-configure.html)
-- The Kanboard webhook url is displayed in **Settings > Integrations > Postmark**
+Just follow the [official documentation about inbound email processing](http://developer.postmarkapp.com/developer-process-configure.html).
+Basically, you have to forward your own domain or subdomain to a specific Postmark email address.
+
+The Kanboard webhook url is displayed in **Settings > Integrations > Postmark**
 
 Kanboard configuration
 ----------------------
@@ -52,4 +27,3 @@ Troubleshootings
 ----------------
 
 - Test the webhook url from the Postmark console, you should have a status code `200 OK`
-- Double-check requirements mentioned above