Luckily, I have found it this time in iOS 12.
If you open Settings>Notifications>Mail, and scroll to the bottom, you will find a section specifically devoted to favorite Mailboxes.
Perseverance paid off, I think.
[doublepost=1528225427][/doublepost]
Please have a look at the configuration available in
Settings>Notifications>Mail>Favorite Mailboxes>...
[doublepost=1528225483][/doublepost]
Please check the configuration available in Settings>Notifications>Mail>Favorite Mailboxes>.
It might fix your issue.
[doublepost=1528225537][/doublepost]
Please check the configuration available in Settings>Notifications>Mail>Favorite Mailboxes>.
It might fix your issue.