When someone registers to my site, the system sends and email to admin@changeme.com
where do i change this email?

also, where do i change the mail from where it is sent?

Never mind. I solved it.
Sorry to bother. I tried to delete the thread.

I'm sure that someone else will have the same question. I hope that you found that the email address used is that of the Site (Portal) Administrator. That assignment is done on the Site Settings page.