Organizing emails for custom domain migrated to icloud.com

Issues Organizing email for custom domain migrated to icloud.com

Recently I migrated a custom domain to iCloud.com, apparently the system does not allow the creation of a mailbox for the custom domain emails, they are all commingled under the iCloud mailbox -- that is strange as it defeats the purpose of a custom domain, but I may be able to handle if someone has found found a fix to this "feature."

The second issue I have on my Mac Mail app I don't have the custom domain email as "From" option, but it shows on my iPhone and iPad.