If Outlook is not displaying your emails in the correct order when viewing them by conversation or thread, there are several options to troubleshooting the issue:

• Check the conversation sort order: Select the conversation sort order (most recent or collapse conversations) to see if the conversation messages display correctly.
• Check group by settings: In folder view, click View settings > Group by (if it's applied) and re-apply the group by option, then check if the messages are sorted correctly.
• Restart Outlook: Restart Outlook and see if the messages are sorted correctly.