Remember to Check Your Junk Email Folder

I very rarely check my junk e-mail folder at work since I presume that everything there is just spam.  I estimate that I immediately delete at least 80% of my work e-mail and 90% of my personal e-mail since I can see from the header that it is just advertisements.  This afternoon I looked at my junk e-mail and found an assignment that a chemical engineering student sent to me last week.  I just don't understand how it got there, but in the future I will quickly peruse that folder before I delete it.