Find your outgoing server IP addresses.

functions.php

<?php

/**
 * Add this to your functions.php and then call your site URL with "get_my_server_ip" in your query.
 * e.g.  https://www.example.com/?get_my_server_ip=1
 */
if ( isset( $_GET[ 'get_my_server_ip' ] ) ) {
	add_action( 'init', function () {
		echo 'Server IPs:<br/>'.implode( '<br/>', array_unique( [
				wp_remote_get( 'https://api.ipify.org' )[ 'body' ],
				wp_remote_get( 'https://api6.ipify.org' )[ 'body' ],
			] ) );
		die();
	} );
}