is domain1.com the only site on the server? Or is a different domain (e.g. domain.com) the main server domain.
The reason I asked is I just had a problem similar, in that i had domain.com, I would add domain1.com, and domain1.com would show domain.com content. Change index.html on the domain.com to see if this is indeed the case.
The problem was, as till pointed out, that I didn't have the server's IP setup in the system settings, and so since I had * selected as the IP - it was resolving to the main domains page, and not that of the user/domain that i had created.