So let's say I have me@mydomain1.com which is it's own Apple ID (same apple ID as the email address that I'm using) and then I have me@mydomain2.com - which also is a separate Apple ID currently but I want to use that domain with iCloud+ (but I only have iCloud+ on mydomain1.com so I want to add mydomain2.com in here) - also for consolidation purposes I'd rather have all my domain emails in one iCloud account. Is this even possible to do since I already had created another Apple ID with me@mydomain2.com? I thought about deleting this Apple ID but noticed you said NOT to do that. I simply just want to add a domain that I own into mydomain1.com's iCloud account but it isn't letting me since it's already registered to an Apple ID. I don't pay for iCloud on that Apple ID so I can't just set it up there (and even if I could it would be annoying to have a separate inbox for this one). Also, I don't want to add it as a family sharing account because that seems unnecessary. Is there any way to do this? Seems crazy that Apple wouldn't allow a way to make this easier - I would have never created an AppleID on this other domain if I knew this was going to be the case...Yes you can, you just have to use the icloud account associated with that Apple ID me@mydomain.com. You can’t add mydomain.com as a custom domain to another Apple ID/icloud account and use me@mydomain.com as an address.
I’ve had to do exactly that since me@mydomain.com was an Apple ID I had for decades but my primary icloud environment was me@icloud.com. I set up icloud mail at the old me@mydomain.com Apple ID, then made that part of me@icloud.com’s family. It actually works out better since my me@mydomain.com email comes into a separate inbox from my icloud email.
The insanity is that Apple won’t let you delete old unused Apple ID’s or combine them so you HAVE to do as above. Even if you delete the old me@mydomain.com Apple ID (DON’T), you’re forever barred from using that email as a custom email or another Apple ID.
It’s very easy to get yourself in a catch 22 since Apple will let you add mydomain.com to your primary icloud account. You can set up any xxx@mydomain.com emails but as soon as you try to use the old me@mydomain.com, it won’t let you add what is probably the ONE address you Really need.
I went through hell getting this sorted.