Thanks for your quick reply.
But that’s not ok with all the custom types and metaboxes/fields, it’s going to go crazy and send hundreds of emails for a simple field change…
I’ll try to find out another solution related to your idea.
PS: the custom post types are useful for directories, and there you need multiple post types (there will not be too many(as stated above), because we also use categories and specific fields based on the categories and post types)