Sende, motta og organisere e-post i Outlook.com
In the Outlook app, on the same computer where you're getting the DNS error, does the email also contain unknown characters and numbers? Or is it normal?
For your signature to be compromised, your email needs to be compromised as well. The laptop with Windows 11 is unrelated to this problem.
You can't sync your Mac on Windows. You can sync Microsoft 365 resources and files using OneDrive, but you can't sync your Mac (Contacts, app data, emails).