Hi,
Sure you can use mod_rewrite to redirect https to another site.
BUT, the client will get a warning about visiting a secure site that is using a certificate issued for another site.
So I guess you have to buy a new certificate for
www.123.com and install it.
To use SSL vhosts in apache you need a recent version of both apache and openssl and the SSLStrictSNIVHostCheck directive. Take a look
here for details
Regards