This evening (UK time), Apple is facing an outage with iCloud Mail, along with other services such as iCloud Calendar and iCloud Keychain which may be seeing slower than usual speeds. However, iCloud Mail is facing an issue since 08:57 PM BST. Just from having a check on Twitter, other users are seeing the same issue with symptoms relating to emails unable to be sent and received, with macOS showing no error messages, but iOS showing error messages in the bottom system tray.

For more up to date information, check Apple’s System Status webpage here.