In Classic Outlook for Windows (including Office Home and Business 2024), the colored circles with sender initials in the message list are not controlled by a simple on/off setting in the Reading Pane options. Classic Outlook’s layout is based on the Navigation Pane, Folder Pane, message list, and Reading Pane, and the available customization in the UI does not include enabling or disabling avatar/initial “chips” in the message list.
If those colored circles are not appearing, this is because the current Classic Outlook build and view configuration do not support that avatar-style display in the same way as the new Outlook or Outlook on the web. There is no documented setting in the provided material to turn this feature on for Classic Outlook, so it cannot be enabled there via standard options.
To adjust what is visible in Classic Outlook, only the documented layout elements can be changed (Navigation Pane buttons, Folder Pane, Reading Pane position/visibility), but not the sender-initial circles in the message list.
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