How to set up saving mail in The bat?

Question

Mail client

Hello. Such a question: at our enterprise, everyone has The Bat mail client. Everything would be fine, but we have 2 mail accounts per 20 people, due to the hindsight of the previous system administrator. So, there are a lot of letters, they are all addressed to different people and always from different people, so the sorting rule will not work here. It happens that some necessary letters are deleted by users (I don’t know why they need it, honestly), is it possible to configure the client to save all mail inside itself so that when deleted from the mailbox, the letters remain in the client?