Can't Access Previously Read Email In Mail Folder


This morning I received an email with an attachment. I read it and put it in one of my Mail folders. But, when I tried to access that same email later in the day, I got the spinning beachball of death. More specifically, I clicked on the folder that the email was placed in, the folder opened and the index bar read: "Indexing 3 of 15: blah, blah, blah" and the beachball spun endlessly. Incidentally, this message 3 of 15 is NOT the same message I received this morning. I've had to force quit a number of times to get out of this. I've rebooted, tried accessing the folder offline, nothing seems to work.

Is the file corrupt? I'd rather not lose this email/attachment as it contains information that I need for future reference. Any tips on how I might access this email?