Ever encounter an issue where you add a new cPanel user, and you receive the following error.
Failed: Account Restore Failed: “Account failure: Failed to create the account: (XID 9tgcb4) “<user>” is a reserved username on this system. at /usr/local/cpanel/Whostmgr/Accounts/Create.pm line 646.
Below is how to correct this issue.
According to the following documentation
There 3 locations that cPanel refers to when checking for "reserved" usernames.
While you can "remove" the user from the aliases files, removing the names from Core.pm is not recommend and would likely be overwritten on a cPanel update.
Once the file is updated, the username will be available for use.