Assume that you have a mailbox in a Microsoft Exchange Server 2013 environment that has cumulative update 7 installed. You receive multiple emails from the same SMTP address, but have different display names. When you download these emails at the same time in conversation view in Microsoft Outlook 2016 for Mac or Microsoft Outlook for Mac 2011, all of the emails from the same SMTP address are displayed with the same display name.
This issue occurs because the cache key of message participants is the SMTP address. Therefore, if messages came from multiple senders who use the same SMTP address and the messages are displayed in conversation view, all these messages are displayed with the same display name.