Can't log in in iCloud on iMac but in the web

I changed my email address from *************

I cannot change on my iPhone and my iMac the iCloud Account because i can't log in with old.de

I can login on the web with new.de and all my account information is available and transferred,

How can I get rid of old.de on iMac and iPhone?

How can I just log in?

Thanks a lot

Thomas

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