As spotted by Bleeping Computer, Microsoft has published a new service alert related to Outlook. Labelled as issue EX1189359 and titled "Users may be unable to open Excel files attached to email ...

Sometimes, problems in Office applications occur due to some problematic add-ins. This can be the case with you. To check this, disable all add-ins in Excel and then save the file. If this works, you ...

Microsoft is working to resolve a known issue that prevents some users from opening Excel email attachments in the new Outlook client.