Deleted Mail Alias still gets mail

An Alias just points to the Original account, so someone sending to "youralias@someserver.com" will lookup the list of aliases linked to you "it's reallyme@someserver.com" & send it to "it's reallyme@someserver.com", but fil the To: field with "youralias@someserver.com".

I imagine you'd have to edit it on the Server somehow...

Create or change an alias

1. In the Mail app  on your Mac, choose Mail > Settings, then click Accounts.
2. Select an account, then click Account Information.
3. Click the Email Address pop-up menu, choose Edit Email Addresses, then do one of the following:

• • Add an alias: Click the Add button , then enter a name and email address.
  • Edit an alias: Click the Full Name or Email Address field, then change the name or email address.
  • Remove an alias: Select an alias, then click the Remove button .

I've had this problem for a few years now with a deleted alias. I can send email to the alias from my other email account and it goes through every time. I've called apple several times about it and each time they say they are looking into it but it never gets resolved.

Hackers know how to get it by...

They're likely using a BCC: list besides the To: form.