Apple is merging Sign in with Apple and Hide My Email under one domain
Apple is consolidating both features under private.icloud.com, with existing addresses continuing to work as normal.
Apple is unifying the email domains used by Sign in with Apple and iCloud+ Hide My Email under a single shared domain, private.icloud.com, later this summer.
New addresses generated by both features will be issued on the new domain going forward. Sign in with Apple addresses were previously issued on privaterelay.appleid.com, while Hide My Email addresses used icloud.com. Both will now use private.icloud.com instead. Existing addresses on the old domains will continue to work and forward mail as normal.
For most users this changes nothing. Developers with apps or websites that use Sign in with Apple will need to make sure their systems accept addresses on the new domain alongside the existing ones, and email service providers will need to update any domain-based filtering rules to include private.icloud.com.
Source: Apple Developers Blog
