This issue is quite common in Outlook versions like Outlook 2007, Outlook 2013 where attachments fail to open. This continues to become an issue when the Outlook temp folder is full and you need to clear it manually. Every time, you close the mail without closing the attachment, the attachment file will not be cleared from the Outlook temp cache folder. OutlookSecureTempFolder or also called as Outlook temporary folder is used to store files like attachments when you open them in Outlook.
