I started having issues last week with my imap account. This little icon that looks like a piece of paper folded on the right corner, appears on some of my emails under the time. When this appears, it will not allow me to open the email. I was told to go under Send/Receive and click on Send/Receive Groups > Define Send/Receive Groups > select Edit and change to (Use the custom behavior defined below). Then select the inbox and click on Download complete item including attachments.
I have done this and restarted my pc and it still doesn't help. What's crazy is that this just started out of the blue.