Would you buy from someone with an “@yahoo.com” e-mail address? I wouldn’t. And the clients I’ve had the most trouble with use yahoo addresses or other free addresses. I understand that you don’t want your regular e-mail address in ads that your run on free ad sites to prevent spam, but lets use some common sense here.
If you don’t buy anything from yahoo’s off line why would you buy from a yahoo online? If you’re serious about your business you have to show it in your actions. The first action to take is to buy your own domain name and use it for all of your e-mails.