How to Group Messages by Thread in Mac OS X Mail

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A discussion spread among dozens of other messages in your Apple's Mac OS X Mail Inbox can be confusing. Luckily, Mac OS X Mail comes with a powerful tool that helps you see messages that belong together in a logical, chronological order.

Group Messages by Thread in macOS Mail and OS X Mail

To read your messages organized by thread in any folder with macOS Mail:

  1. Open the folder in which you want to read mail organized by thread.
    1. macOS Mail will remember your choice for each folder; if you open the folder again later, it will be in the thread organized state again, and changing one folder's setting will have no influence on any other folder.
    2. Threaded view works in both classic and widescreen layouts.
  2. Select View | Organize by Conversation from the menu.
    1. Make sure Organize by Conversation is not checked before you select it; if it is checked, threading is already enabled.

Work with Conversations in macOS Mail

To expand a thread and have all emails in it listed with conversation view in macOS Mail:

  1. Click the number of messages in the thread followed a much greater than sign  in the conversation header (with modern layout) or the right-pointed triangle () in front of the conversation (with classic layout).
    1. You can also press the right arrow key.

To collapse a conversation in macOS Mail:

  1. Click the number of messages in the thread followed by a much greater sign pointing downward (with modern layout) or the downward-pointed triangle () in front of the conversation heading (with classic layout) in the message list.
    1. You can press the left arrow key while viewing any message—or the complete conversation.

To expand or collapse all threads in a folder in macOS Mail:

  1. Make sure conversation view is enabled.
  2. Select View | Expand All Conversations from the menu to explode and View | Collapse All Conversations to collapse all threads.

Choose the Right Options for macOS Mail Conversation View

Did you know you can reverse the order of how emails are arranged in macOS Mail's conversation view, and that it can incorporate messages from other folders?

To pick conversation view settings that work for you in macOS Mail and OS X Mail:

  1. Select Mail | Preferences… from the menu in macOS Mail.
  2. Go to the Viewing tab.
  3. To have macOS Mail find messages in the same thread from folders other than the current one and insert them into the thread where appropriate:
    1. Make sure Include related messages is checked.
      1. Note that emails from other folders—say, Sent—will not be listed in the message list but only appear in the reading pane's full thread view.
      2. You can still act on these messages, e.g. reply to, move or delete them.
      3. Related messages will have listed the folder in which they are located.
  4. To change the order in which emails are shown in the reading pane's conversation view:
    1. Check Show most recent message at the top for reverse chronological ordering and uncheck it for having emails in chronological order from top to bottom.
  5. To have all emails in a thread marked seen as soon as you open the thread in the reading pane's conversation view:
    1. Make sure Mark all messages as read when opening a conversation is checked.
  6. Close the Viewing settings window.

Disable Grouping by Thread in macOS Mail and OS X Mail

To turn off conversation grouping in macOS Mail:

  1. Go to the folder for which you want to disable conversation view in macOS Mail.
  2. Open the View menu.
  3. Make sure Organize by Conversation is checked.
    1. If it is not checked, conversation view is already disabled.
  4. Now select Organize by Conversation from the View menu.

Group Messages by Thread in Mac OS X Mail 1–4

To browse your mail organized by thread in Mac OS X Mail:

  1. Select View | Organize by Thread from the menu.

Should you ever want to turn off this feature again, use the same menu item (to make sure Organize by Thread is not checked).

(tested with Mac OS X Mail 1 and 4 and OS X Mail 9)