Odoo removes the old option to run a fixed server action directly from incoming email servers because emails can now create records across different business areas. Businesses should use automated actions on record creation instead, which is more flexible and avoids mismatches between email processing and the action's target model.

Task: https://www.odoo.com/web#id=58641&view_type=form&model=project.task&action=333&active_id=965&menu_id=4720