Flag in Apple Mail Messages on Mac, and MacBook is a great way to organize your Work and Schedule your Task with Mail Flags. We can add or Rename Flag Lebel and Quickly access by Sort or filter using Flagged mailbox for Mail Messages on the Mail app sidebar. Some of the Mac users Reported Flag is not working in Mail on Mac, Because of Unacceptable changes to the new layout of the Mail app in macOS. Know the Easy ways to Apply new Flags, Change Flag, or Remove Flags from a mail message.
Let’s follow this beginner guide for using Flag on the Apple Mac mail app and Find your answer on Mail Messages with Flag.
Complete Guide on Flags in Mac Mail app
1. Add Flag Column in Mail Mailbox For Messages
Flags Not Showing on Mac mail inbox – “In Column” or “in Mail App Sidebar”
Suppose all your Flagged mail messages are disappeared. Are you unable to find the option to sort Mails with your Flag. We can see flagged Emails in a separate Flag column.
Step 1: Open Mail App on Mac.

Change List Layout Emails to Column Layout in Mail App: From Top Mail App menu > View > Use Column Layout. Also, select “Show Side Preview” if your Messages see the preview at the bottom (Tips For Quickly Read your Email).

Step 3: To add a Flag Column, right-click (Control + Click) on the Top Column Header and Select the Flags Option. How to enable Flags Column in Mailbox on Mac mail app.

Step 4: Flags Added to Column.

Show In Mail app Sidebar:-
Step 1: By Click on the Plus icon next to the Favorites Section,

Step 2: Now, Select Flagged. Click on Ok to add it under the Favorites Section.

Step 3: That’s it.

See, Flagged Mailbox added in Mail app Sidebar.
Now, How to Apply Different Flag to Mail Messages and Use it.
2. Apply Flag on Mail Messages
Flagged Mail messages will be noted with your Marked Flag color in this column. To Add a Flag on Any Mail Message, (Control + Click) right-click on Message > Select Flag [Color] that you quickly identify with the Group or Sort with Flag color.

The second way is to select Mail Message and Go to the Top Mac menu, Messages > Flag > Select Flag that you apply for an Email.

Apply Flag to Multiple Emails at Once: You can Add a Flag to Multiple Mail Messages, Hold the Command Key + Click on Mail Message to select all. Now, Apply Flag by right-clicking (Option + Click) on Selection and Click on Flag.
3. Short or Filter Mail Messages with Flags
Flagged Mailbox will appear on the Mail app sidebar. If you do not see it on the mail app sidebar, then add it first.
Step 1: By Click on the Plus icon next to the Favorites Section,
Step 2: Now, Select Flagged. Click Ok to add under the Favorites Section?
Step 3: That’s it.
To Filter Flagged Emails, Select the Flag color that you used for Flag mail messages. Expand the Flagged Mailbox by clicking on the Arrow icon.

That’s it.
Also Read: How to Sort Mail on Mac
4. Rename Flag on Mac Mail App
We can change the Default Flag name that’s assigned with the Color name. If you are confused with the name of the Flag color, then change it by (Option + Click) right-clicking on Flag > Rename Mailbox.

Type a new Flag name and Hit the Return to Save changes.

4. Re-Order Flags Mailbox on Mac mail app
Apple Mail app on Mac is Customized, Now Even more Clear User interface and Functional. You can now Re-order Flags Mailbox in Sidebar by Select the Mailbox and Drag it into another place.

Using the same techniques, you can move “Flagged” Mailbox entirely or the “Flag” Mailbox as well.
5. Remove Flags from Mac Mail Messages
Yes, we can remove Flag from the Mail message without deleting the mail. Also, we can Change the Flag to a Mail message By right-clicking on the Message From Flag Option on the Mail toolbar, or Messages Menu.
Remove the Flag from Mail message: Select Mail Message > Right Click on > Select Clear Flag. That’s it.

Or, Select and Open mail Message > From the top Toolbar > Click on Flag Toolbox and Select Clear Flag. [Note: in the next step, See how to Add Flag tool on Mail app toolbar]

In the same way from the Message menu, from the top Mac menu bar.
6. Customize Mail Toolbar: Add Flag on Mac Mail App Toolbar
Mac users can customize the Mail app to the End level. To Customize the Mail toolbar, (Option + Click) right-click on the Top Toolbar section from the Email Preview Section.
Step 1: Select the Customize Toolbar option.

Step 2: Here’s all Hidden or inactive Tool. Drag your Favorite item into the Toolbar to add it to the Apple Mac mail app toolbar.

Step 3: Click on Done to save the changes.
That’s it.
From the Flag tool in the Mail app toolbar, Change Flag color, Clear Flag quickly.
Can i Add More Flags to Mac Mail?
No, the User can’t add New Custom Flag colors to Mail Flags. Apple Gives Seven Basic Colors to Flag Message in Mac app. But Yes, we can Rename & Re-order Flags by clicking on the Flag name, Select “Rename Mailbox” and Re-Order by dragging the Flag Mailbox to another place in the Mail app sidebar.
Hope you get the solution for your Mac mail app not showing Flag on Mail messages. Or Unable to filter with Flag.
THANK YOU! It is SO outrageous that some programmer removed FLAGGED from its place of obvious use! SO crazy that one has to add it back in! Thanks again.