Hi @Karen Warren ,
Welcome our forum!
How exactly are your current sent items sorted?
Generally, we can only use the below option to change the order of the emails in Outlook Web App:
Based on my test, i found that we need to sort the emails for all folders. Just like after you set "Sort by Size" for Inbox folder, it will not apply to Sent Items folder. So please first confirm if you set the "Sort by xx" for Sent Items folder.
If the issue still exists, considering the impact of the current browser you are using, please change to another browser to check if there're any differences.
Hope the above help!
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