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You install or update an installation of Microsoft Exchange Server 2019 Cumulative Update 7 or Microsoft Exchange Server 2016 Cumulative Update 18. After the installation, you access an additional mailbox by using the Open another mailbox in Outlook Web App (OWA). If you then try to preview an attachment from the additional mailbox, you receive the following error message:

Something went wrong while the document preview was being created. Please try again later.

If you try to download an attachment from that mailbox, an empty webpage is displayed. The URL for the attachment begins as follows:


This issue is caused by a recent feature change that triggers an HTTP 302 redirect to a static Office 365 URL. This occurs if an additional mailbox is opened in OWA and an attachment is selected for download or preview.


To fix this issue, install one of the following updates:

For Exchange Server 2019, install theCumulative Update 8 for Exchange Server 2019 or a later cumulative update for Exchange Server 2019.

For Exchange Server 2016, install the Cumulative Update 19 for Exchange Server 2016 or a later cumulative update for Exchange Server 2016.


To work around this issue, use either of the following methods:

  • Use the Microsoft Outlook client to open or download attachments from additional mailboxes.

  • Access additional mailboxes by using the OWA light version. To use the OWA light version, add "?layout=light" to the URL of the additional mailbox.

    For example:


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