Antispam Bee is a great spam filtering plugin for WordPress. It's free of charge and ad-free. But the thing is when you apply it for your network, a WordPress multisite with hundred or thousand of blogs, you have to set it up one-by-one. Luckily, I found an easy way to apply the default settings of Antispam Bee for all the blogs, such as disable the spam email notifications or even delete the spam without sending it to the spam folder.
It's quite easy, you just need to open the antispam_bee.php (/path/to/your/wordpress/wp-content/plugins/antispam-bee/) file and modify these lines as following (around line #370, #371):
'flag_spam' => 0,
'email_notify' => 0,