Is it possible to use multiple flags on a single email in Mac Mail?

mail.app

Solution 1:

Mac Mail doesn't allow you to do that, but the Outlook client for macOS does.

enter image description here

Related

Enable SIP without reboot?
How to make spotlight index specific files immediately?
A key combination inserts invisible and festy character in Xcode
How do I access files that are owned by another user?
Quicker way to copy files to a set of different folders for classification purposes
MacBook Pro: Glitch/Copy of closed Window - Graphic card or monitor defect
How to disable sidetone (voice feedback) on USB headset on macOS Catalina?
Synchronise or share .zshrc between accounts
Automator recipe to speed up backups in Time Machine
Is it possible to have two computers that save to iCloud independently with the same Apple ID?
15.4" Retina MacBook Pro (Mid 2012): Broken metal pieces from connector on the motherboard
How do I delete a new Admin account and its data without knowing the old admin password?