If you are using one of the free email services like Hotmail or Yahoo, stop now. If your email address is firstname.lastname@example.org, people are reading that as IDontCareAboutMyBusiness@freemail.com. If you don't know how to fix this, here is the best set-up I have found:
1)Sign up for a domain name with a trusted registrar. Even GoDaddy.com works fine. I like 1and1.com.
2)Go here and follow the instructions for signing up. This is a brand new service that lets you use Google's mail servers with your domain name. Google's mail features are by far the best around, and best of all, they're free!
3)Enjoy your new-found professionalism.