You can safely check an e-mail in Outlook Express by ensuring that Preview Pane is disabled (this should be a PERMANENT safeguard), highlighting the e-mail with one click, right clicking for the Menu and then selecting Properties.
You will then be able to read the header information; the message can then be read (usually) by opening the Message Source tab.
If it's not wanted or from a dubious source, click OK to go back to the still highlighted e-mail and delete using the Delete button on the top bar.
Re the Preview Pane. It's having this enabled that causes viruses to be released as even just clicking on an infected e-mail to highlight it can open a can of worms...