You install or update to 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 this error message:
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 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.
Microsoft is researching this problem and will post more information in this article when it becomes available.