Flagged mailbox on Mac does not sync with flagged mailbox on iPhone
I use flagged mail on my MacBook Air and iMac which sync beautifully but the flagged mailbox on my iPhone remains stubbornly empty. On my laptop and desktop I flag the mail and then file it in the most appropriate folder and these flagged messages are automatically duplicated and grouped in my Flagged Mailbox. This is very handy. However, on my phone, each flagged message is in its appropriate folder synched correctly and flagged but the Flagged mailbox on my phone does not duplicate and group the messages. This is not handy!! Is anyone aware of a fix for this. I am using High Sierra 10.13.3 and iOS 11.2.6
Thank you.
MacBook Air, macOS High Sierra (10.13.3)