Microsoft has started looking into a problem that is preventing users from opening some Excel file attachments with non-ASCII file ...

The cause appears to be the use of non-ASCII characters in file names. Microsoft describes it like so: “Any user may be unable to open Excel files attached to email messages in the new Outlook client ...

New Outlook fails to open Excel attachments with non-ASCII characters in filenames, and shows an error. Microsoft recommends using Outlook on the web or downloading ...