we installed last Thursday CU 18 on a single Exchange 2016. After that we recognized that attachment from shared mailboxes can't be opened anymore. This affects all attachments, download and preview. The problem seems to be that the URL for the attachment ist wrong. When we try to download an attchment a new windows is opened and we're redircted to a url in this format (original domain name is replaced):
I do not understand why this request is getting redirected to office365.com. We do not have an hybrid enviroment or anything like that. "Normal" user accounts does not have any problems. if we forward the affected e-mail from the shared mailbox to a real person, attachment can be opened. Event logs or similar do not show any related anomalies. Any ideas whats going on or how to fix this?
btw, problem exists only in OWA, the same attachment can be opened in Outlook without any problems. The problem also exists with a new shared mailbox.
kind regards Christoph