Question

If a phishing email recipient uses Microsoft Outlook to preview an attachment in a phishing email will this trigger an Attachment Opened in my reports?

Answer

All of our Classic Attachment campaigns contain a 1x1 pixel within the attachment itself. This pixel is used to track if the user opened the email or not when it is download.  Microsoft's preview feature should download this pixel, which will show as Opened in your reports.
 

See Create Classic Attachment Campaign  and Defining Email Opened  for additional information.