WordPress at a glance
function is not described

newblog_notify_siteadmin() WP 3.0.0

Notifies the network admin that a new site has been activated.

Filter 'newblog_notify_siteadmin' to change the content of the notification email.

Hooks in function
Return

true/false.

Usage

newblog_notify_siteadmin( $blog_id, $deprecated );
$blog_id(int) (required)
The new site's ID.
$deprecated(string)
Not used.
Default: ''

Code of newblog notify siteadmin: wp-includes/ms-functions.php VER 5.0.3

<?php
function newblog_notify_siteadmin( $blog_id, $deprecated = '' ) {
	if ( get_site_option( 'registrationnotification' ) != 'yes' )
		return false;

	$email = get_site_option( 'admin_email' );
	if ( is_email($email) == false )
		return false;

	$options_site_url = esc_url(network_admin_url('settings.php'));

	switch_to_blog( $blog_id );
	$blogname = get_option( 'blogname' );
	$siteurl = site_url();
	restore_current_blog();

	/* translators: New site notification email. 1: Site URL, 2: User IP address, 3: Settings screen URL */
	$msg = sprintf( __( 'New Site: %1$s
URL: %2$s
Remote IP address: %3$s

Disable these notifications: %4$s' ), $blogname, $siteurl, wp_unslash( $_SERVER['REMOTE_ADDR'] ), $options_site_url);
	/**
	 * Filters the message body of the new site activation email sent
	 * to the network administrator.
	 *
	 * @since MU (3.0.0)
	 *
	 * @param string $msg Email body.
	 */
	$msg = apply_filters( 'newblog_notify_siteadmin', $msg );

	wp_mail( $email, sprintf( __( 'New Site Registration: %s' ), $siteurl ), $msg );
	return true;
}