How to Flag Messages in OS X Mail

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Flagging makes emails stand out in OS X Mail. © Anne Swoboda; CC BY-SA 2.0 license
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macOS Mail offers colored flags to categorize emails or mark them as important.

Flags in macOS Mail Can Help You Organize in More Ways (and Colors) Than One

You can search. You can file. You can remember.

Of all the ways to set apart an email for later (for a lengthy reply or merely to read it, for example) in MacOS and OS X Mail, what may be the simplest is also possibly one easily overlooked—and surprisingly powerful: flags.

OS X Mail offers a straightforward way to flag and unflag messages. The flag will show prominently when you open the email and make the message stand out in message lists and search, too. Of course, you can use flags in search and smart folders to automate organization.

Behind the simple flag hide many, though: OS X Mail offers seven flags in as many colors. You can add names to the colors to render them more distinct and recognizable.

Colored Flags Are Not Without Drawback

One unfortunate shortcoming of colored flags in OS X Mail is that any message can always be flagged with only one color. You cannot sort and label messages in multiple categories using flags alone.

OS X Mail Flags and IMAP

In OS X Mail on your Mac, flags work the same no matter the account type, and you can use all colors freely.

This is true for IMAP accounts (which synchronize mail and folders across email programs) as well.

On the server—and in other email clients—, all flags will appear as the standard, red flag, though. You cannot differentiate using colors across IMAP installations.

Flag Messages in OS X Mail

To mark an email with a flag in MacOS and OS X Mail for follow-up or so you can find it again easily:

  1. Open or highlight the message you want to flag.
    • You can open an individual message in the reading pane or in its own window, or merely highlight it.
    • To flag multiple emails, highlight all of them in a folder, in a smart folder or in search results.
  1. To apply the standard (red) flag, do one of the following:
    • Press Command-Shift-L.
    • Click the Flag selected messages as button in the toolbar.
      • Note that the button will apply the flag color you last used, not always red.
    • Select Message | Flag | Red from the menu.

Apply a Different-Color Flag or Change the Flag for a Message in OS X Mail

To change the flag color for a message or apply a flag different from the default:

  1. Open the message you want to flag with a custom color.
    • You can also highlight the email—or multiple emails—in any Mail message list, of course.
  2. Do one of the following:
    • Click the down arrow next to the Flag selected messages as.
    • Select Message | Flag from the menu.
  3. Choose the desired flag and color.

Remove a Flag from Email in OS X Mail

To remove the flag from an email in MacOS and OS X Mail:

  1. Open the message you want to unflag.
    • To remove the flag from multiple messages, make sure they are all highlighted in the message list.
  2. To unflag, do one of the following:
    • Press Command-Shift-L.
    • Click the Flag selected messages as button.
    • Select Message | Flag | Red from the menu.

(Tested with OS X Mail 9 and MacOS Mail 10)