Every week we see multiple articles about security researchers who abuses some part of the tech stack to do something weird that shows the danger in this sort of thinking.
I believe it's easy to spoof emails from the .com|disabled domain. Receiving messages, I agree, seems harder. Maybe spoof an unencrypted DNS response at the right moment? No need to actually register a domain when DNS is spoofable.[1]
If you really need to use a hack like that to disable an email, consider adding some code to your email sending logic that skips such email addresses (and always use that logic). Otherwise clever hackers have a foothold to try their tricks against.