If she's had the email for a while, it may be that the layout has been changed and emails from the same user are grouped together possibly? I'm just guessing. May or may not be the case.
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Thank you for the reply. I have learned that the email shows correctly on mobile devices (no old emails). That leads me to believe the issue is probably something within Outlook and has nothing to do with 365, correct? I asked the client to login through email.domain.com in the web browser and see if the inbox is only showing new emails. To me that would at least eliminate the issue being a 365 issue and leads me to believe it is something within Outlook. Do you agree?