Mail problems

Hello,
I'm in big troubles.

I created webspace and site.
Also I turned on mail for that webspace, but I'm receiving "Mail delivery system". 3 different types.
Those reports are attached.
One is that sender sent virus and it's rejected by remote server.
I open that message, and in zip file I see there is .js.

Can you help me with steps how to diagnose what could be a problem, and how to solve it?
Thank you.