Can I add numbers on my iCloud email address?

So, I can't change my primary email address at all? Reason I'm asking is, someone else in another state is using my mac.com email address for their financial information. I'm assuming it's he has another email address for his Apple ID. I've had my .mac address since Aoole started it. I keep getting his email alerts and statements for his institutions which is disconcerting and it's also opening up doors for hackers that may be targeting him. I just got a long threatening email from a scammer referencing my mac.com address.