How to stop receiving iCloud subscription expiration emails and verify their legitimacy?

Here is some information you may find helpful:

Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support (CA)

Phishing emails can also be reported by forwarding the email to reportphishing@apple.com, as you said you have done this already which is great! I don’t believe you will ever hear back about them

or receive any verification whether the email

was legitimate or not, this information is likely used to strengthen spam filters for iCloud email users. Referencing the article

above would be the best way to identify the emails.

These signs can help you identify phishing emails:

• The sender’s email or phone doesn’t match the name of the company that it claims to be from.
• The email or phone they used to contact you is different from the one that you gave that company.
• A link in a message looks right, but the URL doesn’t match the company’s website.2
• The message looks significantly different from other messages that you’ve received from the company.
• The message requests personal information, like a credit card number or account password.
• The message is unsolicited and contains an attachment.

Cheers!

Let me pile on--- They're fake.