Huge email mystery. Receiving the same email, sometimes months apart. Maybe PHP? Maybe VPS server?

So I built a website where customers can request a quote. The mystery is that client will receive the quote and then days, weeks, sometimes months later they will receive the quote again. Exact duplicate of the original email BUT the customer is not resending it. This does not happen with every quote, just some.

Here is the form:

		<form action="request-quote-submit.php" method="GET">
			<p><label for="txtname">Name: </label><input type="text" name="txtname" id="txtname"> *required</p>
			<p><label for="txtphone">Phone: </label><input type="tel" name="txtphone" id="txtphone"> *required</p>
			<p><label for="txtemail">Email: </label><input type="email" name="txtemail" id="txtemail"></p>
			<p><label for="txtaddress">Address: </label><textarea name="txtaddress" id="txtaddress" rows="2" cols="50"></textarea></p>
			<p><label for="txtproblem">How can we help? </label><textarea name="txtproblem" id="txtproblem" rows="6" cols="50"></textarea></p>
			<input type="submit" value="Submit">
		</form>

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On the request-quote-submit.php page I currently have this:

<?php
$name = $_GET['txtname'];
$phone = $_GET['txtphone'];
$email = $_GET['txtemail'];
$address = $_GET['txtaddress'];
$problem = $_GET['txtproblem'];

require_once('class.phpmailer.php');
$mail = new PHPMailer();
$mail->IsSMTP(); 
$mail->SMTPDebug  = 0;
$mail->SMTPAuth   = true;                  
$mail->SMTPSecure = "tls";                 
$mail->Host       = "mail.smtp.com";      
$mail->Port       = 2082;                   
$mail->Username   = "***"; 
$mail->Password   = "***";   
$mail->SetFrom($email, $name);
$mail->AddReplyTo($email,$name);
$mail->Subject    = "A new request for quote!";
$mail->AltBody    = "To view the message, please use an HTML compatible email viewer!"; // optional, comment out and test

if ($name == "" or $phone == "") {;?>
<div class="container padding_30_0 text-center"><p><?php echo "Both name and phone number are required. Please hit the back button and try again.";?></p></div>

<?php } else {

$mail_body = "The following information was filled out on the request a quote form: <br>"; 
$mail_body .= "Name: " . $name . "<br>"; 
$mail_body .= "Phone: " . $phone . "<br>"; 
$mail_body .= "Email: " . $email . "<br>"; 
$mail_body .= "Address: " . $address . "<br>"; 
$mail_body .= "Problem: " . $problem . "<br>"; 

$mail->MsgHTML($mail_body);
$mail->AddAddress('eben@***.com');
$mail->AddAddress('tracee@***.com');
$mail->AddAddress('rgfrancis@***.com');
if(!$mail->Send()) {
  echo "Mailer Error: " . $mail->ErrorInfo;
} else {
  echo "<br>Thanks for filling out our form. Someone from *** will be in contact shortly.";
}
$mail->clearAddresses();
?>
<?php };?>

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I say currently because in the example I will show below I was using php mail and my VPS Server's SMTP (InMotion Hosting) to send the original and when the client received the duplicate emails 5 months later I has already switched to using phpmailer and SMTP.com.

Here are the headers for the emails:

Original email sent 9/15/16:

Received: from [10.115.3.14] (helo=smtp.maileig.com)
        by bosmailscan05.eigbox.net with esmtp (Exim)
        id 1bkbns-00017l-Tv
        for tracee@***.com; Thu, 15 Sep 2016 14:54:32 -0400
Received: from bosmailscan05.eigbox.net
        by bosmailscan05.eigbox.net (Dovecot) with LMTP id
KhzdBVTu2ldLCwAAi0ZokQ
        for <tracee@***.com>; Thu, 15 Sep 2016 14:54:33
-0400
Received: from vps17664.inmotionhosting.com ([104.152.109.190])
        by bosimpinc14 with bizsmtp
        id juuW1t02F46WzJ001uuXJl; Thu, 15 Sep 2016 14:54:32 -0400
Received: from maconw5 by vps17664.inmotionhosting.com with local (Exim
4.87)
        (envelope-from <maconw5@vps17664.inmotionhosting.com>)
        id 1bkbnV-0003ZL-NJ; Thu, 15 Sep 2016 14:54:29 -0400
Return-Path: <maconw5@vps17664.inmotionhosting.com>
Reply-To: <quotes@***.com>
From: <quotes@***.com>
To: <tracee@***.com>,
        <eben@***.com>
Subject: A new request for quote!
Date: Thu, 15 Sep 2016 14:54:09 -0400
Message-ID: <E1bkbnV-0003ZL-NJ@vps17664.inmotionhosting.com>
MIME-Version: 1.0
Content-Type: text/plain;
        charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
X-Mailer: PHP/5.5.32
X-EN-OrigIP: 104.152.109.190
X-EN-OrigIP: 104.152.109.190
X-EN-IMPSID: juuW1t02F46WzJ001uuYM9
X-EN-IMPSID: juuW1t02F46WzJ001uuXJl
Thread-Index: AQKcDhIehAOeggMWj4QeFhH5aFp1jw==
X-PHP-Script: ***/request-quote-submit.php for
24.214.117.144
X-OutGoing-Spam-Status: No, score=0.0
X-AntiAbuse: Original Domain - ***.com
X-AntiAbuse: Primary Hostname - vps17664.inmotionhosting.com
X-AntiAbuse: This header was added to track abuse, please include it with
any abuse report
X-AntiAbuse: Sender Address Domain - vps17664.inmotionhosting.com
X-AntiAbuse: Originator/Caller UID/GID - [504 504] / [47 12]
X-Get-Message-Sender-Via: vps17664.inmotionhosting.com: authenticated_id:
maconw5/from_h
X-Authenticated-Sender: vps17664.inmotionhosting.com:
quotes@***.com

Duplicate from 2/3/17

Received: from mailer120.gate86.rs.smtp.com ([74.91.86.120])
                by bosimpinc11 with bizsmtp
                id gFvl1u0032bmscS01FvmYS; Fri, 03 Feb 2017 10:55:46 -0500
Received: from [10.115.3.11] (helo=smtp.maileig.com)
                by bosmailscan01.eigbox.net with esmtp (Exim)
                id 1cZgDC-0001J9-9j
                for tracee@***.com; Fri, 03 Feb 2017 10:55:46 -0500
Received: from [104.152.109.190] ([104.152.109.190:33249] helo=***.com)
                by rs-ord-mta01-in1.smtp.com (envelope-from <trappjp@***.com>)
                (ecelerity 4.1.0.46749 r(Core:4.1.0.4)) with ESMTPSA (cipher=ECDHE-RSA-AES256-SHA)
                id 6E/65-14601-008A4985; Fri, 03 Feb 2017 15:55:44 +0000
Received: from [192.168.80.11] ([192.168.80.11:36688] helo=rs-ord-mta01-in1.smtp.com)
                by rs-ord-mta03-3.smtp.com (envelope-from <trappjp@***.com>)
                (ecelerity 4.2.1.55028 r(Core:4.2.1.12)) with ESMTP
                id 62/91-21793-008A4985; Fri, 03 Feb 2017 15:55:44 +0000
Received: from bosmailscan01.eigbox.net
                by bosmailscan01.eigbox.net (Dovecot) with LMTP id 7foRBRWnlFi4QAAA1eVBQw
                for <tracee@***.com>; Fri, 03 Feb 2017 10:55:46 -0500
Return-Path: <trappjp@***.com>
Reply-To: "John Trapp" <trappjp@***.com>
From: "John Trapp" <trappjp@***.com>
To: <eben@ebengraystreeservice.com>,
                <tracee@***.com>
Subject: A new request for quote!
Date: Fri, 3 Feb 2017 10:55:44 -0500
Message-ID: <5942ec573f67ce318ae2823ceb9db67b@ebengraystreeservice.com>
MIME-Version: 1.0
Content-Type: multipart/alternative;
                boundary="----=_NextPart_000_00A4_01D27E2C.E75F50D0"
X-Priority: 3
X-Mailer: PHPMailer 5.2 (http://code.google.com/a/apache-extras.org/p/phpmailer/)
Thread-Index: AQFO0fh54lFyge0MDpvXAbQpFZcwNA==
X-EN-OrigIP: 74.91.86.120
X-EN-IMPSID: gFvl1u0032bmscS01FvmYS
X-MSFBL: aKZrqTrIw6kDvd8MGUvVyQ9PtRZepGeMpRIzqgipmmQ=|eyJiIjoiNzRfOTFfODZ
                fMTIwIiwiZyI6Im1haWxfc2hhcmVkX3Bvb2wiLCJyIjoidHJhY2VlQGViZW5ncmF
                5c3RyZWVzZXJ2aWNlLmNvbSJ9
X-Report-Abuse: SMTP.com is an email service provider. Our abuse team cares about your feedback. Please contact abuse@smtp.com for further investigation.
X-SMTPCOM-Tracking-Number: 40cfa312-234f-4b3c-83df-079927d88d60

Duplicate from 2/16/17

Received: from mailer111.gate86.rs.smtp.com ([74.91.86.111])
                by bosimpinc14 with bizsmtp
                id lScx1u02H2Q7pa201ScyZQ; Thu, 16 Feb 2017 09:36:58 -0500
Received: from [10.115.3.14] (helo=smtp.maileig.com)
                by bosmailscan01.eigbox.net with esmtp (Exim)
                id 1ceNB4-0004et-QB
                for tracee@***.com; Thu, 16 Feb 2017 09:36:58 -0500
Received: from [104.152.109.190] ([104.152.109.190:33182] helo=***.com)
                by rs-ord-mta02-in1.smtp.com (envelope-from <trappjp@***.com>)
                (ecelerity 4.1.0.46749 r(Core:4.1.0.4)) with ESMTPSA (cipher=ECDHE-RSA-AES256-SHA)
                id 10/B9-11339-909B5A85; Thu, 16 Feb 2017 14:36:57 +0000
Received: from [192.168.80.21] ([192.168.80.21:59464] helo=rs-ord-mta02-in1.smtp.com)
                by rs-ord-mta01-out1.smtp.com (envelope-from <trappjp@***.com>)
                (ecelerity 4.2.1.55028 r(Core:4.2.1.12)) with ESMTP
                id A9/BB-17054-909B5A85; Thu, 16 Feb 2017 14:36:57 +0000
Received: from bosmailscan01.eigbox.net
                by bosmailscan01.eigbox.net (Dovecot) with LMTP id XgYiBfu4pVhgeQAA1eVBQw
                for <tracee@***.com>; Thu, 16 Feb 2017 09:36:58 -0500
Return-Path: <trappjp@outlook.com>
Reply-To: "John Trapp" <trappjp@***.com>
From: "John Trapp" <trappjp@***.com>
To: <eben@***.com>,
                <tracee@***.com>
Subject: A new request for quote!
Date: Thu, 16 Feb 2017 09:36:56 -0500
Message-ID: <616aec7a7aed8be218d3c7c11b5ef3cc@***.com>
MIME-Version: 1.0
Content-Type: multipart/alternative;
                boundary="----=_NextPart_000_0035_01D28839.B141AB30"
X-Priority: 3
X-Mailer: PHPMailer 5.2 (http://code.google.com/a/apache-extras.org/p/phpmailer/)
Thread-Index: AQIFJfqtvboSiHkKfo5IdrKI0/gqQA==
X-EN-OrigIP: 74.91.86.111
X-EN-IMPSID: lScx1u02H2Q7pa201ScyZQ
X-MSFBL: PA1Ssj768Db3mSjK0FMQFliilwwbYj3EWvKXDtJiZr4=|eyJnIjoibWFpbF9zaGF
                yZWRfcG9vbCIsImIiOiI3NF85MV84Nl8xMTEiLCJyIjoidHJhY2VlQGViZW5ncmF
                5c3RyZWVzZXJ2aWNlLmNvbSJ9
X-Report-Abuse: SMTP.com is an email service provider. Our abuse team cares about your feedback. Please contact abuse@smtp.com for further investigation.
X-SMTPCOM-Tracking-Number: e0cd8eb4-54cc-4203-96c7-2860a94af5d3
X-SMTPCOM-Sender-ID: 5024167

Now the way I look at it, it could be three things:

Error in PHP page - Not sure how because you would actually have to run both the form page and submit page again to make the email send

The hosting server that the page sits on which is InMotion, even though I am not using the SMTP on the server anymore (when duplicates where sent). Don't know enough to understand this.

Actual SMTP service, but then again I was using two different services during this whole thing.

Does anyone have any ideas. Client is getting pissed.

Thanks in advance