I am not sure what you mean by that, but I found a solution (on Reddit of all places!)
TheLittles wrote:
Odenzo Said:
"Can I have wild-card email address with customer domain, e.g. anything@foo.mine gets delivered"
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Use an Alias for your DomainL
You need to sync your eMAil address with the correct credentials. Elsewise, it will not sync. Once synced, see if using an alias would be an option for you.
What is Catch-All:
It allows you to accept all emails to a domain that don't match an existing mailbox.
How it is useful:
I have long had the habit of using purpose/service specific email addresses. For example, in signing up for an iPhone pre-order I may use iphone.preorder.verizon@mydomain.com. Given I did not actually create a corresponding user/mailbox for the address, with catch-all available and enabled, all emails to the address will simply be forwarded to my main mailbox.
Through this, I was able to hold various entities accountable for leaking my email addresses, i.e. when I start receiving spam through them, or when they appear in data dumps. It is always funny to see companies/services trying to argue they are not responsible for either leaking or selling user data when the email addresses were 'created' for and used solely by them.
With Catch-All now available, we have access to unlimited email 'aliases', and we can 'blacklist' them when they 'go bad' via iCloud Mail server-side filter "Addressed-to" rules, sending emails to them straight to the bin.
Yay!
PS. Catch-All can be enabled via Settings > Apple ID > iCloud > Custom Email Domain > [Your Domain] > Allow All Incoming Messages
Turned out I needed to restart my iPhone to see it, then suddenly it showed up on iCloud too.