To whom can i send an email complaint about very poor service?

Depends on the nature of your dissatisfaction There's a corporate model and stores can't stray from it. If, however, you were mistreated by an associate, then the best course of action is to approach the store manager.

Corporate has no email address that the public can send to. I think corporate dosen't want to hear complaints

I'd recommend going directly to corporate myself, sometimes those box stores are buddy buddy and take care of each other.