Hey there LAM09,
Thanks for reaching out! We understand you're having trouble connecting to iCloud Mail on your Mac.
To start, make sure you look over over the details below in case you need to make any changes:
1. Check the system status of iCloud Mail.
2. Check that you turned on iCloud Mail:
* On your Mac, open the Mail app then choose Mail >Preferences. Click Accounts, then select your iCloud account in the sidebar. Under Account Information, make sure that the account is turned on and the status is online.
* On your iPhone, iPad, or iPod touch, go to Settings > [your name] > iCloud and check that Mail is turned on.
3. Make sure you that haven't exceeded your iCloud storage limit. If you exceed your iCloud storage limit, learn how to make more space available in iCloud.
4. Make sure that you're using the latest version of software on your device.
If you need additional help, continue with the troubleshooting steps here:
If iCloud Mail isn't working - Apple Support
Take care!