Goal: only oneserver.com should be forwarded to otherserver.com
Problem: also x.com and y.com are forwarded.

<VirtualHost 123.123.123.123:80>
    RewriteEngine on
# redirect all to oneserver.biz towards http://www.otherserver.com/
    RewriteCond %{HTTP_HOST}   !^oneserver\.biz [OR]
    RewriteCond %{HTTP_HOST}   !^www\.oneserver\.biz [OR]
    RewriteCond %{HTTP_HOST}   !^$
    RewriteRule ^/(.*)         http://www.otherserver.com/ [L,R]
# the others should go for the normal docroot.
    ServerName www.parked.com
    ServerAlias oneserver.biz *.oneserver.biz x.com *.x.com y.com *.y.com
    ServerAdmin webmaster@webmaster.com
    DocumentRoot /home/parked/public_html
    RewriteEngine on
    RewriteRule         ^/stats/?$              /cgi-bin/awstats/awstats.pl [L,R]
</VirtualHost>