您可以使用transition_post_status 函数，然后获取用户并向所有用户发送电子邮件。

这是一个示例代码，它没有经过测试。但这会让你从这个开始。

function wcs_send_mail_on_publish_category_posts( $new_status, $old_status, $post ) {

    global $post;

    if ( \'publish\' !== $new_status or \'publish\' === $old_status ) return;

    if ( in_category( array( \'12\', \'34\' ) ) ) {

        $subscribers = get_users( array ( \'role\' => \'subscriber\' ) );
        $emails      = array ();

        foreach ( $subscribers as $subscriber )
            $emails[] = $subscriber->user_email;

        $body = sprintf( \'Hey there is a new entry! See <%s>\', get_permalink( $post )  );

        wp_mail( $emails, \'New entry!\', $body );

    }

}

add_action( \'transition_post_status\', \'wcs_send_mail_on_publish_category_posts\', 10, 3 );