email not being sent

I'm having problems sending email. When registred or ordering and when I email myself a coustomer I never get a mail message. I can get incoming mail but not outgoing. Person I hired to do this said "It seems the problem is on your server although I can't figure it out." I paid the guy to set it up he did but not this part. So is it my ISP internet or my webhost.

ISP is changing if not already from comcast to time warner. Or my host but not sure what they can do. Since this scrip fourm is here I asked here. Should I use another cart? Or can someone help me out. I just started a small business registred my business on 8/11 but this is hurting me as I spent many hours going at this. :(

What are the settings you have in the Admin> Configuration> Email Settings?

The problem is not likely your ISP, as the emails are generated from within the Zen Cart software running on your host.

Who is your host?
Are you hosted on a Windows server or Linux?
What version of Zen Cart are you using?
And, as Kim suggested, what are the settings in Admin->Config->Email Options ?