PHPMailer not working consistently - php

Question

I have a web app using PHP, MySQL, and PHPMailer to send emails. The issue I am having is PHPMailer will send some of the emails, but not always. I'm thinking maybe it is because different list of emails have data issues? Below is my code that loops through the email addresses and send some, but not all the emails. I have tried to catch errors, but I can't see any in the logs.
How can I debug what is going on, and why some don't send?
else if($current_version == 'PROD'){
date_default_timezone_set('America/New_York');
require 'PHPMailer-master/PHPMailerAutoload.php';
$pageURL = 'xxxxxx';
$subject = "xxxxx ";
$body = "xxxxxx \r\n";
$body .= "xxxxx \r\n \r\n";
$body_html = str_replace("\r\n","<br/>",$body);
try {
$mail = new PHPMailer();
$mail->isSMTP();
//Enable SMTP debugging
// 0 = off (for production use)
// 1 = client messages
// 2 = client and server messages
$mail->SMTPDebug = 0;
$mail->Debugoutput = 'html';
$mail->Host = 'smtp.gmail.com';
//Set the SMTP port number - 587 for authenticated TLS, a.k.a. RFC4409 SMTP submission
$mail->Port = 587;
//Set the encryption system to use - ssl (deprecated) or tls
$mail->SMTPSecure = 'tls';
$mail->SMTPAuth = true;
$mail->Username = "xxx#xxxx.com";
$mail->Password = "xxxx";
$mail->setFrom('xxxxx#xxxx.com', 'xxxx');
$mail->addReplyTo('xxxx#xxxx.com', 'xxxx');
$mail->Subject = $subject;
$mail->Body = $body_html;
$mail->AltBody = $body;
$sql_email_list = "SELECT email FROM tbl_email
WHERE distro_name='xxxxs'
AND is_active='Y' ";
$result_email_list = mysql_query($sql_email_list);
$num_email_list = mysql_num_rows($result_email_list);
$lost_email_list = mysql_result($result_email_list,0,'email');
$lost_email_array = explode(";",$lost_email_list);
foreach ($lost_email_array as $key => $val){
$mail->AddAddress($val);
if($carrier_email_flag_global == 'ON'){
$mail->send();
$mail->ClearAllRecipients();
$mail->ClearAttachments();
echo '<hr>Email Sent to: '.$val;
}
}
$sql_email_one = "SELECT table2.email
FROM table1
INNER JOIN table2 ON table1.cntct = table2.cntct_id
WHERE id='$id' ";
$result_email_one = mysql_query($sql_email_one);
$num_email_one = mysql_num_rows($result_email_one);
for($iiz=0;$iiz<$num_email_one;$iiz++){
$one_email = mysql_result($result_email_one,$iiz,'email');
$mail->AddAddress($one_email);
if($carrier_email_flag_global == 'ON'){
$mail->send();
$mail->ClearAllRecipients();
$mail->ClearAttachments();
echo '<hr>Email Sent to: '.$val;
}
}
} catch (phpmailerException $e) {
echo $e->errorMessage(); //Pretty error messages from PHPMailer
echo '<hr>ERROR 001';
} catch (Exception $e) {
echo $e->getMessage(); //Boring error messages from anything else!
echo '<hr>ERROR 002';
}
}