Laravel version 8.64.0, PHP version 8.1.0, strtolower(): Passing null to parameter #1 ($string) of type string is deprecated

[Salem-Matloob-Al-Twami]

To my humbling understanding,

strtolower(): Passing null to parameter #1 ($string) of type string is deprecated.
This issue is there because we create an object of Swift_SmtpTransport with

$transport = new SmtpTransport(
$config['host'],
$config['port']
);

on MailManage.php

and we on the constructor of Swift_SmtpTransport
public function __construct($host = 'localhost', $port = 25, $encryption = null)
hence, $encryption would be null and we call

    $this->setEncryption($encryption);

on it!!

I had to downgrade my PHP to 8.0 to avoid this issue.

Is there any other fix to it?

Thank you

[Salem-Matloob-Al-Twami]

need to upgrade Swiftmailer 6.3