Apple Users

Correct me if I am wrong, anyone.
And check with an Apple support person.

If you have icloud email, you must have an iCloud ID.

On your phone, go to Settings -> Passwords
You will need your phone pass or touch or Face ID to see them

That will have your account and password info.

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As for Comcast, anything that someone paid for has a fighting chance of staying alive. Free accounts can and do vanish for no reason and it can take forever to find a real person to unlock an account. Two email accounts are a boon because one can go down at any time, even Apple's. With iOS you can set up fake accounts that forward to your real email ( "Hide my email" ) and that's handier than throwaway accounts (getnada.com and others) to deal with spammers.