With the preview panel off, you can highlight the message then select Properties from the File menu (top right). However, the from address is almost certainly either spoofed (ie. not real) or is that of an innocent party whose identity has been lifted from someone's address book (eg. BadTrans virus).
But well done for trapping it yourself. A-V software will only stop known viruses, and then only if you update regularly and faithfully. Someone has to be the first to be attacked.