I have just added the ability to use an alternate NNTP server for postprocessing. This would allow you to use all NNTP connections form 1 provider for binaries and backfill and use all the NNTP from another provider for postprocess.
Change www/config.php and add the second provider details and the select yes in admin edit.
define('NNTP_USERNAME', 'username');
define('NNTP_PASSWORD', 'password');
define('NNTP_SERVER', 'news.newshosting.com');
define('NNTP_PORT', '443');
define('NNTP_SSLENABLED', true);
define('NNTP_USERNAME_A', 'username');
define('NNTP_PASSWORD_A', 'password);
define('NNTP_SERVER_A', 'ssl-eu.astraweb.com');
define('NNTP_PORT_A', '443');
define('NNTP_SSLENABLED_A', true);