No live changes

I need a client to save my messeages, while they will stay at the server for another device. In this moment, when I delete a e-mail from eM client, this e-mail is also deletet from server - and if I delete it from servet, it is deletem from eM client.
What kind of setup do I need to change?
Thank you very much.

Yes that’s how a normal modern IMAP / Exchange email account works. When you delete email from one device, all devices will sync and are deleted the same. The idea is only delete email if you really want to delete it. You can always get it back though from your deleted / trash bin.

If you don’t want that, you have to setup the older POP email account where you set to "Leave a copy of messages on the server) for X amount of days (on all devices) which then downloads the emails to each devices and then leaves a copy of the messages on the server.