Php mail() email sendouts arriving in gmail account but not in regular email accounts
I have a php script that sends out emails with attachments once people have submitted some information. I receive these emails in my gmail inbox with no problem. However, when I use my personal email address or my work email address the email is never delivered. Is this a problem with my script (below) or some setting I have on the server. 
The server is the clients managed server with a plesk control panel so I don't have access to the php ini file.

    //define the receiver of the email
	$to = 'test@test.com';
	//define the subject of the email
	$subject = 'Email with Attachment';
	//create a boundary string. It must be unique
	//so we use the MD5 algorithm to generate a random hash
	$random_hash = md5(date('r', time()));
	//define the headers we want passed. Note that they are separated with \r\n
	$mime_boundary = "<<<--==+X[".md5(time())."]";
	
	$path = $_SERVER['DOCUMENT_ROOT'].'/two/php/';
	$fileContent =  chunk_split(base64_encode(file_get_contents($path.'CTF_brochure.pdf')));
	

	$headers .= "From: info@example.org.uk <info@poundsandpennies.org.uk>\r\n";  

	$headers .= "MIME-Version: 1.0\r\n";
	$headers .= "Content-Type: multipart/mixed;\r\n";
	$headers .= " boundary=\"".$mime_boundary."\"";



	
	$message = "This is a multi-part message in MIME format.\r\n";
	
	$message .= "\r\n";
	$message .= "--".$mime_boundary."\r\n";
	
	$message .= "Content-Type: text/plain; charset=\"iso-8859-1\"\r\n";
	$message .= "Content-Transfer-Encoding: 7bit\r\n";
	$message .= "\r\n";
	$message .= "Email content and what not: \r\n";
	$message .= "This is the file you asked for! \r\n";
	$message .= "--".$mime_boundary."" . "\r\n";
	
	$message .= "Content-Type: application/octet-stream;\r\n";
	$message .= " name=\"CTF-brochure.pdf\"" . "\r\n";
	$message .= "Content-Transfer-Encoding: base64 \r\n";
	$message .= "Content-Disposition: attachment;\r\n";
	$message .= " filename=\"CTF_brochure.pdf\"\r\n";
	$message .= "\r\n";
	$message .= $fileContent;
	$message .= "\r\n";
	$message .= "--".$mime_boundary."\r\n";

	//send the email
	$mail_sent = mail($to, $subject, $message, $headers);
	//if the message is sent successfully print "Mail sent". Otherwise print "Mail failed"
	echo $mail_sent ? "Mail sent" : "Mail failed";
Php mail() email sendouts arriving in gmail account but not in regular email accounts
===

I have a php script that sends out emails with attachments once people have submitted some information. I receive these emails in my gmail inbox with no problem. However, when I use my personal email address or my work email address the email is never delivered. Is this a problem with my script (below) or some setting I have on the server. 
The server is the clients managed server with a plesk control panel so I don't have access to the php ini file.

    //define the receiver of the email
	$to = 'test@test.com';
	//define the subject of the email
	$subject = 'Email with Attachment';
	//create a boundary string. It must be unique
	//so we use the MD5 algorithm to generate a random hash
	$random_hash = md5(date('r', time()));
	//define the headers we want passed. Note that they are separated with \r\n
	$mime_boundary = "<<<--==+X[".md5(time())."]";
	
	$path = $_SERVER['DOCUMENT_ROOT'].'/two/php/';
	$fileContent =  chunk_split(base64_encode(file_get_contents($path.'CTF_brochure.pdf')));
	

	$headers .= "From: info@example.org.uk <info@poundsandpennies.org.uk>\r\n";  

	$headers .= "MIME-Version: 1.0\r\n";
	$headers .= "Content-Type: multipart/mixed;\r\n";
	$headers .= " boundary=\"".$mime_boundary."\"";



	
	$message = "This is a multi-part message in MIME format.\r\n";
	
	$message .= "\r\n";
	$message .= "--".$mime_boundary."\r\n";
	
	$message .= "Content-Type: text/plain; charset=\"iso-8859-1\"\r\n";
	$message .= "Content-Transfer-Encoding: 7bit\r\n";
	$message .= "\r\n";
	$message .= "Email content and what not: \r\n";
	$message .= "This is the file you asked for! \r\n";
	$message .= "--".$mime_boundary."" . "\r\n";
	
	$message .= "Content-Type: application/octet-stream;\r\n";
	$message .= " name=\"CTF-brochure.pdf\"" . "\r\n";
	$message .= "Content-Transfer-Encoding: base64 \r\n";
	$message .= "Content-Disposition: attachment;\r\n";
	$message .= " filename=\"CTF_brochure.pdf\"\r\n";
	$message .= "\r\n";
	$message .= $fileContent;
	$message .= "\r\n";
	$message .= "--".$mime_boundary."\r\n";

	//send the email
	$mail_sent = mail($to, $subject, $message, $headers);
	//if the message is sent successfully print "Mail sent". Otherwise print "Mail failed"
	echo $mail_sent ? "Mail sent" : "Mail failed";