Mac mini: iCloud Mail sending fails

Hello Community,

I switched to Cloud+ on a Mac mini M4 Pro running macOS 26.1. As a result, when sending an iClode (...@me.com) email, I get an error (Server response: Client host rejected: Access denied), and the email doesn't send. I also can't temporarily disable iClode mail on the Mac mini. However, I also have an iPhone running macOS 26.1 connected to my local network, and iClode (...@me.com) emails work fine on it.

Thank you for your time.