Update documentation about incoming emails

doc/en_US/create-tasks-by-email.markdown

@@ -18,28 +18,17 @@ All complicated works are already handled by those services.
 Incoming emails workflow
 ------------------------
 
-1. You send an email to a specific address, for example **something+myproject@inbound.mydomain.tld**
+1. You send an email to a specific address, for example **myproject@inbound.mydomain.tld**
 2. Your email is forwarded to the third-party SMTP servers
 3. The SMTP provider call the Kanboard web hook with the email in JSON or multipart/form-data formats
 4. Kanboard parses 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, for example **kanboard+project123**
-- The string defined after the plus sign must match a project identifier, for 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
--------------------------
+Notes
+-----
 
 - The Kanboard web hook is protected by a random token
 - The sender email address must match a Kanboard user
-- The Kanboard project must have a unique identifier, for example **MYPROJECT**
 - The Kanboard user must be a member of the project
+- Kanboard is able to convert only simple HTML emails to Markdown
+- New tasks are automatically created in the first column
+- Refer to the documentation of each plugin for the configuration