There are a few ways to find a person’s work email address. One way is to do a quick search on the Internet using the person's full name, along with what you think the last part of the company email address might be (try typing it in a format like this: @hercompanyname.com). Another way is to search the Internet using various combinations of the person's full name, as well as the company name (try typing in something like: Kathy_Jones@hercompanyname.com#ENDIF or kjones@hercompanyname.com#ENDIF).
Alternatively, email addresses can be found by searching popular professional networking sites like LinkedIn. And, lastly, some people resort to the old-fashioned, low-tech method of calling a company and asking for an email address.