Email from Apple

Without seeing the email, I can't give you a definite answer. You should take a look at Recognise and avoid phishing messages, phoney support calls and other scams – Apple Support

Apple will never ask for any bank information, personal information, passwords etc in an email as a rule of thumb.

If you do have an eligible promotion you can ignore the email and claim the promotion via the steps at Get Apple TV+ – Apple Support which directs you to https://offers.appletvapp.apple/

If you've bought a new, eligible Apple device you should be able to sign up for a free Apple TV+ trial, I don't see any reason why this email shouldn't be legitimate, I know the offer also appears in your Settings of your iPhone if you feel more secure signing up that way, if it is an iPhone.

https://www.apple.com/promo/pdf/EN_US_ATV+_Promo_TandCs.pdf