I have a client whose IMAP accounts I have set up to link with Odoo.

Odoo is getting filled up with span and personal messages they do not want.

I want to set up their system so that only those incoming messages which are a reply to an outgoing message from within Odoo are automatically posted within Odoo. So far as all other incoming messages are concerned, I want my clients users to be able to filter these through their standard email system and choose whether or not to forward them to Odoo.

What is the simplest way to achieve this objective?