In case of Emails, several posts will be created if there are more than 1 recipients, so trying to cancel duplicates Internet Message Posts is impossible (or some customers will never receive the emails)

erp5_crm: display standard preview on Mail Message only if internet_message_post_module isn't installed

To prevent race-condition in a multi-node environement (ie: 2 activity nodes load the afterAllowExport activities for 2 Posts having the same reference)

The attachment field now uses the property aggregate_document_title of Event.

erp5_interface_post: interface_post_workflow prevents having several versions of the same post in the exportable queue

It will be used to differenciate attachments from Mime Post.

erp5_interface_post contains ***_post_modules, which purposes are to track posts that go out and in ERP5, without any processing.