Disable read confirmation on mail for mac or iOS

Have you tried using Outlook for iOS / macOS? This is highly recommended if you are using 365 or an Exchange email server.

The macOS Mail app does not send requests for read receipts nor does it have an option to ignore read receipt requests. Despite your 365 email having these features turned off, the way that Mail connects to 365 is not the same way that Outlook connects. You should discuss this issue with your email administrators. There may be additional settings they can tweak on the 365 admin console.

Are you confusing Message Application with Apple Mail Application. Messages application Read Receipt can be turned off within the Messages Application >> Preferences. AFAIK - the stock Apple Mail Application does not have that feature as you described.

Your comment is all over the place so I don’t know what to make of it.

Wbat makes you think it sends a “read confirmation”, and to whom?

There is no such thing as “internal” or “external” e-mail. Maybe there is a break down in communication, perhaps you are thinking of outbound (ie mail you send) vs inbound (mail you receive)?

Finally downloading content or not is completely unrelated to read confirmation - which, assuming you mean in the sense of sending a reception confirmation (similar to what Messages does) is something that Mail has never done, as far as I know.

So perhaps you’d like to clarify all of this.