When you receive an email message that has multiple attachments that was created in Microsoft Outlook 2013 or Outlook 2010, you may receive one of the following error messages when you open an attachment.
Word found unreadable content in <File Name>. Do you want to recover the contents of this document? If you trust the source of this document, click Yes.
File <File Name>: file format is not valid.
PowerPoint found a problem with content in <File Name>. PowerPoint can attempt to repair the presentation.
If you trust the source of this presentation, click Repair.
Note If the email contains attachments of only the same extension, you may notice that content is not in the correct file.
When multiple attachments are sent from Outlook 2013 or Outlook 2010, the attached files are renamed as other attached files. This is a known issue in Outlook that occurs when emails are auto-saved or saved with multiple attachments.
To resolve this issue for Outlook 2013, install the January 12, 2016, update for Outlook 2013. For information about this update, click the following article to view it in the Microsoft Knowledge Base:
3114500 January 12, 2016, update for Outlook 2013 (KB3114500)
To resolve this issue for Outlook 2010, install the October 13, 2015, update for Outlook 2010. For information about this update, click the following article to view it in the Microsoft Knowledge Base:
3085604 October 13, 2015, update for Outlook 2010 (KB3085604)