iOS 18.2, released in December 2024, introduced major changes to the way that mail can be viewed in the Mail app. I think the optional changes, outlined in the link below, can be confusing for VoiceOver and low vision users and recommend you don't use the new automatic categorisation feature until you have studied its behaviour carefully and decided whether or not it is for you. I don't use categorisation myself and don't recommend it but, if it suits you, that's great. All the information on this website assumes you are using the original, list view and it will be applicable to category view with only minor modifications.