Email has opened up a whole new avenue of communication for businesses. Spam filters will get rid of a good amount of unsolicited email offers. Make sure to alert your employees to not sign up to any websites using their work email address.
The best way to keep business and non-business related email separate is to impress upon your employees to keep their work email address for work matters only.
Cousin-who-moved-overseas is not as big a problem as dodgy email attachments, of course. It's severely damaging to a company's reputation. Genuine companies would never ask for these details via email. If in doubt, please contact your bank or the company in question.
Email can be an asset, if used well. Email is not the be-all and end-all of business...
The Pros and Cons of Email in the Business World
Just remember that there is nothing wrong with having your name in the business name.