Send Mail to Multiple Address in Cakephp 3 : Cannot modify an existing config

I am trying to send email to multiple recipient address in cake php 3.

my codes are :

$this->loadModel('AsIndividualDetails');
$EmailDetails = $this-> AsIndividualDetails->find('all',['fields'=>'email']);
$EmailDetails = $EmailDetails->toArray();
                
  foreach ($EmailDetails as $key => $a) {
      
        $this->loadModel('DomainEmailDetails');
        $DomainEmailDetails = $this-> DomainEmailDetails->find('all')->first();
        $DomainEmailDetails = $DomainEmailDetails->toArray();
        $host     = 'ssl://'.$DomainEmailDetails['host_name'];
        $username = $DomainEmailDetails['user_name'];
        $password = $DomainEmailDetails['user_password'];
        $port     = $DomainEmailDetails['port'];
        $email_to = $a['email'];
        $senderName = 'abc';
        $email_id   ='xyz110@gmail.com';
    
        Email::configTransport('WebMail', [
                                                          'className' => 'Smtp',
                                                          'host' => $host,
                                                          'port' => $port,
                                                          'timeout' => 30,
                                                          'username' => $username,
                                                          'password' => $password,
                                                          'client' => null,
                                                          'tls' => null,
                                            ]);
                      ////////// SEND MAIL 
                      $email = new Email('WebMail');
                      $email  ->template('default','default')
                              ->emailFormat('both')
                              ->from([$username => $senderName])
                              ->to($email_to)
                              ->replyTo($email_id)
                              ->subject('Client Message');
                      $response = $email->send('My msg');
    
                      if($response){
                          echo 'success';
                      }else{
                          echo 'failed';
                      }
    
} 

When I run this script just only one mail send successfully and after that an error has come :

Cannot modify an existing config "WebMail" 

How to solve this error and send mail to all recipient mail address.

Define configuration before foreach() .