Hi @Rob018 ,
Welcome to our forum!
According to your description, I'm afraid that the closest way to your requirement is to enable "Show as Conversations" in the Outlook client. And it can also make all of the sent and received messages in a group by subject, as shown in the below figure. You can click the message on the left in the group to make it displayed in reading pane.
Based on my test, I found that the difference from Outlook for web is in the following: when opening the reading pane, on Outlook for web, all conversation emails are displayed on the right side without clicking the email of the group on the left side; but in the Outlook client, we can manually select the email of the group on the left side to display the message in the reading pane on the right. In my opinion, it is precisely in this way that the corresponding email can be clearly displayed.
In the outlook client, we can also make other settings for the conversation view for easier use. For more information about Conversation view, please refer to: View email messages by conversation.
Hope the above help!
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