public function send_mail( $to, $subject = '', $message = '', $headers = array(), $attachments = array() ) {

		if ( $this->options[ 'static_options' ][ 'mail_to_chunking' ][ 'chunking' ] === TRUE ) {
			// the next group of recipients
			$send_next_group = array();
			if ( array_key_exists( 'send_next_group', $this->options[ 'static_options' ] ) ) {
				$object_id       = $this->options[ 'static_options' ][ 'object' ][ 'id' ];
				$send_next_group = $this->options[ 'static_options' ][ 'send_next_group' ][ $object_id ];
			}

			if ( $this->options[ 'send_by_bcc' ] ) {
				$headers[ 'Bcc' ] = $this->get_mail_to_chunk( $headers[ 'Bcc' ], $send_next_group );
			} else {
				$to = $this->get_mail_to_chunk( $to, $send_next_group );
			}
		}

		foreach ( $headers as $k => $v ) {
			$headers[] = $k . ': ' . $v;
			unset( $headers[ $k ] );
		}

		return wp_mail(
			$to,
			$subject,
			$message,
			$headers,
			$attachments
		);
	}