If you are using a mail service provider like SendGrid, it can create a proxy that may cause issues when you try to validate emails, for example.

To fix this, go to your bootstrap app file and add this line to the middleware:

$middleware->trustProxies(at: '*');

Then it should look like this:

// bootstrap/app.php
<?php

use Illuminate\Foundation\Application;
use Illuminate\Foundation\Configuration\Exceptions;
use Illuminate\Foundation\Configuration\Middleware;

return Application::configure(basePath: dirname(__DIR__))
    ->withRouting(
        web: __DIR__.'/../routes/web.php',
        commands: __DIR__.'/../routes/console.php',
        health: '/up',
    )
    ->withMiddleware(function (Middleware $middleware) {
        $middleware->trustProxies(at: '*');
    })
    ->withExceptions(function (Exceptions $exceptions) {
        //
    })->create();