I own an e-mail address that I used to use as an ID. apple says someone owns it. can't be what do I do?

because of some corruption years ago, my e-mail address was no longer allowed so i changed username for apple id to another e-mail. the old address is still absolutely owned by me. apple says on the one hand it's not an apple id, then on the other says it is and can't be used. I am at a loss. I've researched this and can't find an answer as to what to do?