How do I include the Company Name in emails sent by Exchange Server 2003?

I’ve just deplayed SBS 2003 Premium. Exchange working well but when a user sends an email to an outside party, the email header only contains that users name followed by the email address is brackets i.e. First Name + Last Name (emailaddress@company.com).

Does any one know how I can get the company name to appear in the header? so it looks like this First Name + Last Name + Company Name(emailaddress@company.com).

Thanks guys.

Pete