You create a new email message in Microsoft Outlook 2016 for Mac or Outlook for Mac 2011, attach an .eml file that was created in Microsoft Outlook Express, Windows Live Mail, or Apple Mail to the message. You then send the message, and the .eml attachment is not displayed correctly on the recipient's email client.
This issue occurs because Outlook for Mac does not encode the .eml attachment correctly.
To work around this issue, use a compression utility to add the .eml file to an archive. Then, attach the archive file to the Outlook for Mac email message, and send the message.
Note On Mac, you can use the Compress option on the File menu in Finder.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
The issue that is described in the "Symptoms" section occurs when you attach .eml files that were created in Microsoft Outlook Express, Windows Live Mail, or Apple Mail or that were generated by those programs.