Deleting old messages/attachment from Messages app on Mac

Welcome back elektrobank,

We're happy to try to clarify. If you have Messages in iCloud set up on a device, any deletions that occur on that device will occur on iCloud and across all other devices that are using the service. To prevent those actions and delete messages only on your Mac, you would need to disable Messages in iCloud on the Mac.

We hope this helps!

Greetings elektrobank,

We see you have questions related to your use of Messages in iCloud and are happy to offer some information we hope helps.

Per our page Use Messages in iCloud, "Messages in iCloud are updated automatically, so you always have the same view everywhere you use iMessage. When you delete a message, photo, or conversation on one device, it’s removed from all of your devices." There are further directions on that page if you wish to disable Messages in iCloud for only a specific device and how that would impact your experience.

Cheers!