Outlook inbox and OWA inbox have different content

Thomas Walters 21 Reputation points
2021-11-17T18:18:41.927+00:00

I have a user who has different content in the Outlook inbox and in the OWA inbox. It is not that one is a subset of the other, there is different content. There are two or three messages today that exist in both, otherwise completely different. This situation is the same whether using Outlook in online mode or Exchange Cached mode. There does not seem to be any rhyme or reason as to what goes where. Mimecast is in the mix. If I go to the Mimecast archive, I see all of the messages from both Outlook and OWA. Has anyone seen this before? More importantly, has anyone seen this and fixed it?

TIA

Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Thomas Walters 21 Reputation points
    2021-12-21T12:30:05.027+00:00

    An update to this issue. While the same account was being used, there were two mailboxes created, one on-prem and the other in O365. Found this article: https://learn.microsoft.com/en-us/exchange/troubleshoot/user-and-shared-mailboxes/mailbox-exists-exo-onpremises?WT.mc_id=365AdminCSH_SupportCentral

    The article focused on saving the O365 mailbox, while I needed to save the on-prem mailbox. The solution was to remove the user's O365 license in AAD. The Office 365 mailbox was deleted automatically and mail flow was returned to normal.

    HTH anyone with this issue.

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