I get the same error message. I suspect the root-cause is the same policy issue.
I just finished speaking with an Apple Support advisor about this error message ”This email is already in use with another Apple ID.” when trying to re-assign a Custom Domain Email Address from one family sharing member to another..
Steps to Reproduce
- I own a custom domain (foo.com). I successfully added it to my iCloud account for use with Custom Domain Email.
- I assigned a custom domain email address to myself (bat@foo.com).
- Then I realized I meant to assign that address to a different family member. My family member is part of my iCloud Family Sharing.
- I removed the address from my individual iCloud user account.
- Then I tried adding it to my family members iCloud user account. Adding failed, showing the error message, ”This email is already in use with another Apple ID.”
Apple Support Team (1st & 2nd Attempt)
After two different calls with the front-line support team, which had to be over the phone (having to repeatedly spell the domain name and the custom email address and my icloud email address and the family member’s icloud email address…not fun) I my issue was escalated to a what they called a “senior advisor”.
Senior Apple Support Advisor Explanation
The senior advisor took time to investigate and research the issue for a day and setup a callback time. In the end, they found that the root-cause was an iCloud Policy. To paraphrase:
If a Custom Domain Email Address has been previously assigned to an iCloud user, the Custom Domain Email Address must be deleted and left unused for one (1) year before it can be assigned to another iCloud user. Even if the two iCloud users are members of the same iCloud Family Sharing.
I imagine this policy is meant to prevent some form of abuse.
Wishing won’t help, but…
Having self-hosted my email for a very long time, I was very surprised I couldn’t immediately re-assign the email to a different user.
- I wish the waiting period was shorter, such as 24-hours or worst 30-days.
- I wish the iCloud Custom Domain Email product had much more detailed Apple Support documentation.
- I wish the iCloud Custom Domain Email setup flow had more specific and detailed instructions and warnings to inform users and help avert this type of issue.
