Delete an email alias but keep Apple ID?

See all about aliases in these documents:

iCloud: About your @icloud.com, @me.com, and @mac.com email addresses https://support.apple.com/en-us/HT201771

Using your @icloud.com email address https://support.apple.com/en-us/HT201342

I've always though you could not delete one that that ends in @mac.com or @me.com email. But, this read which may be in error or out of date says you can, although you can't add it back.

You can change or delete an email alias, but if you delete an @mac.com or @me.com email alias, you can't add it back to your iCloud account. I've never tried to delete on though.

To make things complete, also see: Use email aliases on iCloud.comhttps://support.apple.com/en-nz/guide/icloud-ipad/mm6b1a490a/icloud

You are very welcome. What you mention is unfortunate, but sometimes happens. You may want to create a new Apple ID (see below), a 3rd-party one. But, check these security documents out first to see if you can live with the current situation.

If you think your Apple ID has been compromised https://support.apple.com/en-us/HT204145

Security and your Apple ID https://support.apple.com/en-us/HT201303

iCloud security overview  https://support.apple.com/en-us/HT202303

Ways to keep your information safe on Mac https://support.apple.com/en-gb/guide/mac-help/mh11402/mac

Using app-specific passwords https://support.apple.com/en-us/HT204397

UseTwo-factor authentication for Apple ID https://support.apple.com/en-us/HT204915

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Also, Check your Apple ID device list  (https://support.apple.com/en-us/HT205064) and remove any device that shouldn't be signed in using the steps in the link.

If there are none that shouldn’t be signed in, then you should not have a problem at this point. But, if an unauthorized device is signed in, Change your Apple ID password https://support.apple.com/en-us/HT201355 

Here is What to do after you change your Apple ID or password https://support.apple.com/en-us/HT204071

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See How to create a new Apple ID https://support.apple.com/en-us/HT204316. See the data implications below.

Some of these things may apply even though not changing an Apple ID: What to do after you change your Apple ID or password https://support.apple.com/en-us/HT204071

 Keep in mind that some things available under a first Apple ID will not be available under a new Apple ID. For example, you won’t be able to transfer anything purchased from the App and iTunes Stores to the new ID. And, there are other issues to be addressed.

And see what Eric Root says on this matter here https://discussions.apple.com/thread/251343949 and

what Winston Churchill says about it here: https://discussions.apple.com/thread/7452747

You are welcome. If they hijacked the alias, changing your Apple ID password should cut off their access to the address.  You can also add 2 Factor Authentication to your account for more security.

Link to contact Apple Support in the article.

Apple ID has been compromised.      

Security and your Apple ID.      

 Apple ID Password Change.     

 What to do after you change your Apple ID or password - Apple Support    I suggest doing this before you change your Apple ID or password.

Apple ID -Two-factor authentication          

 Two Factor Authentification availability.     

 Apple ID - Using app-specific passwords.     

Apple ID - Two Step Verifications FAQ    

If you create/use a new Apple ID, you will lose access to some of your data and the purchases made with your existing Apple ID.

Ask Apple ID Support. See the Apple Support articles below for contact information.  

Apple ID - Official Apple Support.    

Contact Apple for help with Apple ID account security - Apple Support.   (Link doesn’t always load)  

Get Support          Work through the screens to get a chat option. 

Apple Support schedule phone call

https://twitter.com/AppleSupport.          People have posted it may take an hour or more to get a response.

You can't remove/change @iCloud.com, @me.com or @mac.com aliases.

iCloud - Create or change email aliases.   

I see this: "Note: You can’t delete or turn off a primary @icloud.com email address." But, that's not the same as deleting it.

Incidentally, which support URL are you talking about?

I'm glad that you got it sorted and that Apple support did such a great job. Be safe.

You are welcome.