ProxyPanel/app/Notifications/AccountActivation.php

<?php

namespace App\Notifications;

use Illuminate\Bus\Queueable;
use Illuminate\Notifications\Messages\MailMessage;
use Illuminate\Notifications\Notification;

class AccountActivation extends Notification
{
    use Queueable;

    private $url;

    public function __construct($url)
    {
        $this->url = $url;
    }

    public function via($notifiable)
    {
        return ['mail'];
    }

    public function toMail($notifiable)
    {
        return (new MailMessage)
            ->subject(__('Verify Email Address'))
            ->line(__('Please click the button below to verify your email address.'))
            ->action(__('Verify Your Email Address'), $this->url)
            ->line(__('If you did not create an account, no further action is required.'));
    }
}