Hi smoketx,
Thanks for coming to Apple Support Communities for help today setting up your email with the custom email domain for iCloud Mail.
It sounds like you have followed this page of the iCloud User Guide: Set up a custom email domain for iCloud Mail on all your devices.
Please note:
"After you add a custom email domain to iCloud, you can send and receive email on your iPhone, iPad, iPod touch, Mac, and Windows computer when you turn on iCloud Mail in iCloud settings. You can also access your mail on iCloud.com."
Next you'd follow: Set up iCloud for Mail on all your devices.
"Set up iCloud for Mail on your Mac
- On your Mac, choose Apple menu > System Preferences, click Apple ID, then click iCloud.
- If you want to send and receive iCloud Mail on your Mac, select Mail.
- If you want to keep Mail settings up to date across your devices, turn on iCloud Drive, then click Options and select Mail. The following settings stay up to date:
- Blocked senders (for all macOS devices)
- Email address suggestions (for all iOS, iPadOS, and macOS devices)
- Flag names (for all macOS devices)
- Mail rules (for all macOS devices)
- Signatures (for all macOS devices)
- Smart Mailboxes (for all macOS devices)
- VIPs (for all iOS, iPadOS, and macOS devices)
To view your iCloud Mail, open the Mail app. Click a mailbox or folder in the iCloud section.
For more information on how to use Mail on your Mac, see the Mail User Guide for Mac."
Have a fantastic day!