Expected response code 354 but got an empty response "500" in laravel 7

While i'm trying to send email by using laravel 7 but i got an error..!

Code : (.Env file)

MAIL_DRIVER=smtp
MAIL_HOST=smtp.mailtrap.io
MAIL_PORT=2525
MAIL_USERNAME=4ef712cdfb3044
MAIL_PASSWORD=5aafacfc3884df
MAIL_ENCRYPTION=tls
MAIL_FROM_ADDRESS=null
MAIL_FROM_NAME="${APP_NAME}"

Code : ResetPasswordController

namespace App\Http\Controllers;

use App\User;
use Illuminate\Http\Request;
use App\Mail\ResetPasswordMail;
use Illuminate\Support\Facades\Mail;

class ResetPasswordMail extends Mailable
{
public function send($email)
    {
        Mail::to($email)->send(new ResetPasswordMail());
    }
}

That error is : " Expected response code 354 but got an empty response ". Kindly please help me friends.

Thanks for Advance..