Per-folder push notifications for incoming emails not working after updating to iOS 12

I have just updated to iOS 12 and I'm having problems with push notifications for incoming e-mails: I have a couple of Office 365/Microsoft Exchange accounts which have a complex folder structure and a lot of server-side rules to sort the incoming mail into those folders. On iOS 11 and earlier, I was setting up my pushed mailboxes so that I get notifications about new email in the folders I care most about. Since updating my iPhone to iOS 12, those notifications stopped coming in - I'm getting notifications about new mail in the inbox but not in other folders. It looks like pushing the emails down to the device works because when browsing through the list of folders in Mail app I see the expected number of unread mails in each folder but when a new email arrives, I don't get a notification. I checked the notification and push settings and everything looks correct. I tried rebooting my iPhone and deleting and re-adding the email account but that didn't help. Anybody noticed the same issue? Any hints how to debug this? Apple Support only suggested resetting settings or restoring the device but I'm looking for something less invasive than that if possible...