Don't send email messages with enclosures unless you really know the recipient isn't a civilian. And don't ever send Word documents as email messages. Never do it. The viruses make it look like the message is coming from a friend. Oy, such bad advice.
Email is wide open.
No firewalls there. But even the Web isn't safe as long as you can download apps and run them. Microsoft could help , they make the most popular and vulnerable emailer. Email could be as safe as the Web, imho. Last month, I had meetings with dot-coms in all stages of development.