iPhone 16 and lost access to my personal email

The weekend I upgraded from an iPhone 12 to an iPhone 16 Pro max, I followed the steps to transfer my data over and instead of using from iCloud I just transferred the old iPhone to the new one. On completion I deleted the old phone ready to be traded in when I went on the new phone. It was asking me for passwords for my personal email which is different to the registered one with my iPhone account although it is still an iCloud email address. The situation now is that I am locked out of my email address with nor access to it. The message I received was that they were going to review my case and reply to the email address? Even though I have no access to it has anybody any ideas how I can rectify this? It is my email that is registered with my Doctors and the hospital, which I am a frequent visitor of? Do you recommend I email Apple? If so, does anybody know the correct department? I should contact? Thank you.