To stop emails from Chatter auto-deleting, you need to change the email preferences in your Odoo settings. Here are the steps to follow:

Login to your Odoo account and go to the Settings menu.
Under the General Settings tab, scroll down to the Chatter section.
Click on the "Email" sub-tab.
Under "Email Settings", uncheck the option that says "Automatically delete email from discussions."
Click on "Save" to save the changes.
By disabling this option, all emails sent through Chatter will be saved in the system and will not be automatically deleted. This will allow you to access and review them later on.

Greetings,
Peter