I'd like to echo this request.
I find that messages flagged in AquaMail appear in Outlook with No Date flags. That's okay. And if I un-flag the message, in AquaMail, it becomes un-flagged in Outlook.
However, if a message is first flagged in Outlook, it never shows as flagged in AquaMail. That's bothersome. I'm having to use the Outlook mobile app or the Microsoft To Do app, to handle flagged messages on my phone.
It gets more interesting: If I flag the email in Outlook, with a custom date, the message is not flagged in AquaMail. If I then flag the same message in AquaMail, the Outlook flag changes from its custom date, to No Date. Super-bothersome.