Thanks for the answer! I had realized that yesterday and fixed the problem. My bad. If you are kind to help me: Now I am trying to send a bulk mail and the mail does not reach its destination. 
Melhor falar portguês, ja que voce é português, e eu brasileiro. :-)
Veja o codigo abaixo pf e se tiver alguma observação ...
Valeu.
$from_name = "NeuroTraumaBrasil";
$from_address = "
[email protected]";
$reply_address = "
[email protected]";
$reply_name = "reply";
$error_delivery_address="
[email protected]";
$error_delivery_name="NeuroTraumaBrasil";
	$email_message=new sendmail_message_class;
	$email_message->delivery_mode=SENDMAIL_DELIVERY_QUEUE;		$email_message->bulk_mail_delivery_mode=SENDMAIL_DELIVERY_INTERACTIVE;
	
	$email_message->SetBulkMail(1);
	$subject=$assunto;
	$email_message->SetEncodedEmailHeader("From",$from_address,$from_name);
	$email_message->SetEncodedEmailHeader("Reply-To",$from_address,$from_name);
	
	if(defined("PHP_OS")
	&& strcmp(substr(PHP_OS,0,3),"WIN"))
		$email_message->SetHeader("Return-Path",$error_delivery_address);
		
	$email_message->SetEncodedEmailHeader("Errors-To",$error_delivery_address,$error_delivery_name);
	$email_message->SetEncodedHeader("Subject",$subject);
	$email_message->cache_body=1;		//sem personalizacao de email
	$html_message=$msgHTML;
	$email_message->CreateQuotedPrintableHTMLPart($html_message,"",$html_part);
	
	$text_message="Esta mensagem tem formato HTML, favor utilizar cliente que suporta formato Html.";
	$email_message->CreateQuotedPrintableTextPart($email_message->WrapText($text_message),"",$text_part);
	$alternative_parts=array(
		$text_part,
		$html_part
	);
	$email_message->AddAlternativeMultipart($alternative_parts);
	for($recipient=0;$recipient<count($to);$recipient++)
	{
		$to_address=$to[$recipient]["address"];
		$to_name=$to[$recipient]["name"];
		$email_message->SetEncodedEmailHeader("To",$to_address,$to_name);
		$error=$email_message->Send();
		if(strlen($error))
			break;
	}
	$email_message->SetBulkMail(0);
	if(strlen($error))
		return "Error: $error";
	else
		return "";