This is an old trick. A little while ago someone was putting the EICAR test string in email subject lines, headers, inside PDF files, in mime headers, and in ot

This is an old trick. A little while ago someone was putting the EICAR test string in email subject lines, headers, inside PDF files, in mime headers, and in other random places. He managed to crash a lot of enterprise level AV solutions and email servers. If you want to be a dick, just copy and paste that string everywhere you can. The AV will treat it like a real threat.