I am guessing that you have a "mysite-1.com" folder in the /etc/apache2/sites-available directory. Basically, this is not exactly a drupal question, since the redirections can (and should -if you ask me-) be handled by the server.
Assuming that you have a specific dedicated for the site that you want to redirect, you should change it to something like this:
redirect permanent / http://www.sometothersite.com/
The change should be made to the conf file where the VirtualHost directive resides (the one that is used to describe the site that you want to discontinue). Most commonly the specific directive can be found in the apache2.conf, the httpd.conf or the .htaccess file in the root of your drupal installation.
Notice, that the sample above is not the only way to do it: you can use mod_rewrite too, but keep in mind that you should do it inside the VirtualHost directive.