The feature of scheduled fetch and notifications for mails received in Favorited folders, Threads, and VIP notifications (configuration option provided in Settings>Notifications>Mail) was available for non push mail accounts in iOS 10 and earlier (but was missing in iOS 11). In iOS 12, Apple had added this very essential feature.
Now it has again been removed from iOS 13 betas.
The current design in iOS 13 betas is just the opposite of what is desired.
What is required: configuration options and feature for scheduled fetch and notifications for favourited mail folders & thread mails of non push enabled mail accounts?
What is delivered in iOS 13: the configuration options and feature for scheduled fetch and notifications for non push enabled mail accounts, which were already available in iOS 12, have been removed from iOS 13.
In the absence of this feature, I am missing mails received in favorited folders for non push enabled mail accounts (my mail accounts are IMAP and not push capable or enabled). This defeats the very purpose of having a favorited folder for such mail accounts. The favorited folders and thread mails do not get read on the iOS device as they do not get fetched on schedule and generate no notifications. The mail app in the iOS device is therefore useless and totally unreliable. There is no function fulfilled by the favorited folders as one has to individually open each folder of the mail account (irrespective of whether it is a favorited folder or not) to see if any new mail has been received in that folder (mails are configured to be filtered at the server level and get delivered to various folder at the server level). Alternatively one has to open the mail account (IMAP which does not support push) on a desktop computer to be really sure of whether any mail has been received in any of their folders.