Flag messages
An easy way to keep track of messages is to mark them with a flag. When you do, a mailbox for the flag appears in the Favorites bar and displays messages you mark with that flag.
Add flags to messages: Select one or more messages, click the Flag button
in the Mail toolbar (or use the Touch Bar), then choose a flag. The flag appears in the header of each message.Show flagged messages: In the Favorites bar, click Flagged, then choose a flag. Only messages marked with that flag are shown in the message list. To see all messages in the Inbox again, click Inbox in the Favorites bar.
Rename flags: In the Mail sidebar, click the disclosure triangle next to the Flagged mailbox to show the flags (there must be more than one flag in the mailbox). Click a flag, click it again, then type a new name. For example, you could rename Red to Urgent.
Search for flagged messages: Type a flag name in the search field, then select the suggestion in the Flags category. Or type “flag,” then choose the suggestion in the Status category.
Clear flags from messages: Select one or more messages, click the Flag button in the Mail toolbar, then choose Clear Flag.
A flag mailbox is a type of Smart Mailbox. Learn more about how Smart Mailboxes organize messages.
If you use iCloud Drive, your flag names are available on your other Mac computers that have iCloud Drive turned on. For more information, see Store your desktop and documents in iCloud.