Issues Forwarding Default Address

I've been using cPanel for a while, but am still somewhat a newbie when it comes to it...and am experiencing an issue I just can't seem to work around.

Basically, it involves being able to forward the default address. Let's say that my account username (and default address) are abc123 and the associated domain is cpanel1234.com. I set up a forwarder so that any email sent to abc123@cpanel1234.com is automatically forwarded to my personal email address (since I would assume that is the correct format for the default address, and also since the forwarder requires the @cpanel1234.com to be input). If I now send email to abc123@cpanel1234.com, it works and is forwarded to where I tell it to go.

However, the problem lies in how internal email from cPanel gets sent to the default email address. If I set up a default address for a subdomain, parked domain, or add-on domain, I believe it defaults to abc123 as the default address. However, it seems that when cPanel attempts to send email to just "abc123" it actually ends up going to abc123@xyz.com (where xyz.com is some sort of subdomain that my hosting provider uses for shared hosting - I think). This then ends up not getting forwarded to me, and there doesn't seem to be any way for me to add abc123@xyz.com as a forward in my cPanel since xyz.com is not a domain or subdomain I control.

In fact, it seems that any time cPanel wants to send email to me using my default address, it does so just at "abc123" rather than "abc123@cpanel1234.com" and this causes me to not get the email.

Any idea how I can fix this so even when cPanel sends me email at just "abc123" it still gets forwarded to me?

Thanks! (and sorry for using all the fake email addresses above - just being cautious).