update_option_new_admin_email( string $old_value, string $value )

function update_option_new_admin_email( $old_value, $value ) {
	if ( $value == get_option( 'admin_email' ) || ! is_email( $value ) ) {
		return;
	}

	$hash = md5( $value . time() . wp_rand() );
	$new_admin_email = array(
		'hash'     => $hash,
		'newemail' => $value,
	);
	update_option( 'adminhash', $new_admin_email );

	$switched_locale = switch_to_locale( get_user_locale() );

	/* translators: Do not translate USERNAME, ADMIN_URL, EMAIL, SITENAME, SITEURL: those are placeholders. */
	$email_text = __( 'Hello ###USERNAME###,

You recently requested to have the administration email address on
your site changed.

If this is correct, please click on the following link to change it:
###ADMIN_URL###

You can safely ignore and delete this email if you do not want to
take this action.

This email has been sent to ###EMAIL###

Regards,
All at ###SITENAME###
###SITEURL###' );

	/**
	 * Filters the text of the email sent when a change of site admin email address is attempted.
	 *
	 * The following strings have a special meaning and will get replaced dynamically:
	 * ###USERNAME###  The current user's username.
	 * ###ADMIN_URL### The link to click on to confirm the email change.
	 * ###EMAIL###     The proposed new site admin email address.
	 * ###SITENAME###  The name of the site.
	 * ###SITEURL###   The URL to the site.
	 *
	 * @since WP-MU (3.0.0)
	 * @since WP-4.9.0 This filter is no longer Multisite specific.
	 *
	 * @param string $email_text      Text in the email.
	 * @param array  $new_admin_email {
	 *     Data relating to the new site admin email address.
	 *
	 *     @type string $hash     The secure hash used in the confirmation link URL.
	 *     @type string $newemail The proposed new site admin email address.
	 * }
	 */
	$content = apply_filters( 'new_admin_email_content', $email_text, $new_admin_email );

	$current_user = wp_get_current_user();
	$content = str_replace( '###USERNAME###', $current_user->user_login, $content );
	$content = str_replace( '###ADMIN_URL###', esc_url( self_admin_url( 'options.php?adminhash=' . $hash ) ), $content );
	$content = str_replace( '###EMAIL###', $value, $content );
	$content = str_replace( '###SITENAME###', wp_specialchars_decode( get_option( 'blogname' ), ENT_QUOTES ), $content );
	$content = str_replace( '###SITEURL###', home_url(), $content );

	wp_mail( $value, sprintf( __( '[%s] New Admin Email Address' ), wp_specialchars_decode( get_option( 'blogname' ), ENT_QUOTES ) ), $content );

	if ( $switched_locale ) {
		restore_previous_locale();
	}
}