ok i got a solution for anyone interested,
you cant disable the mail function but you can set a false path to sendmail in the vhosts (within httpd.conf)
example:
<VirtualHost 111.111.1111.111:80>
DocumentRoot /home/ryza
ServerAdmin ryza@ryza.com
ServerName www.ryza.com
Directory Configuration
#######################
<Directory /home/ryza>
shtml & directory indexes.
Options Includes Indexes
basic htaccess
AllowOverride AuthConfig Limit
disable backquotes and bad functions
php_admin_value safe_mode 1
lock them in there dir
php_admin_value open_basedir "/home/ryza"
false sendmail path
php_admin_value sendmail_path "/bin/false"
</Directory>
</VirtualHost>