Php mail not working with more than one recipient - php

Question

How come this piece of php code doesn't work with multiple recipient ?
It only works if $to has only one adress, like:
$to = 'aa#bb.com';
Edit
It works if email adresses are on the same domain.. For instance, if the website is www.example.com, emails such as xxx#example.com will work but yyy#other.com won't.
Solution
PHPMailer. It gives an easy way to configure SMTP.
Here is the initial code
<?php
//define the receiver of the email
$to = 'aa#bb.com, cc#dd.com, ee#ff.com';
// array with filenames to be sent as attachment
$files = array("a.zip","b.c","a.html");
// email fields: to, from, subject, and so on
$from = "mail#mail.com";
$subject ="My subject";
$message = "My message";
// boundary
$semi_rand = md5(time());
$mime_boundary = "==Multipart_Boundary_x{$semi_rand}x";
// headers for attachment
$headers = "From: $from";
$headers .= "\nMIME-Version: 1.0\n" . "Content-Type: multipart/mixed;\n" . " boundary=\"{$mime_boundary}\"";
// multipart boundary
$message = "This is a multi-part message in MIME format.\n\n" . "--{$mime_boundary}\n" . "Content-Type: text/plain; charset=\"iso-8859-1\"\n" . "Content-Transfer-Encoding: 7bit\n\n" . $message . "\n\n";
$message .= "--{$mime_boundary}\n";
// preparing attachments
for($x=0;$x<count($files);$x++){
$file = fopen($files[$x],"rb");
$data = fread($file,filesize($files[$x]));
fclose($file);
$data = chunk_split(base64_encode($data));
$message .= "Content-Type: {\"application/octet-stream\"};\n" . " name=\"$files[$x]\"\n" .
"Content-Disposition: attachment;\n" . " filename=\"$files[$x]\"\n" .
"Content-Transfer-Encoding: base64\n\n" . $data . "\n\n";
$message .= "--{$mime_boundary}\n";
}
// send
$ok = #mail($to, $subject, $message, $headers);
if ($ok) {
echo "<p>mail sent to $to!</p>";
} else {
echo "<p>mail could not be sent!</p>";
}
?>
Here is the final code
// PHPMailer
$mail = new PHPMailer;
// setting up PHPMailer
$mail->isSMTP();
$mail->Host = 'host.com';
$mail->SMTPAuth = false;
$mail->Port = xx;
$mail->setFrom($_POST['email'], $_POST['name']);
$mail->Subject = $_POST['subject'];
$mail->msgHTML($_POST['message']);
foreach($contacts as $contact)
$mail->addAddress($contact['email']);
// If the user has attached some files
foreach ($_FILES as $file)
$mail->addAttachment($file['tmp_name'], basename($file['name']));
$response = array("status" => $mail->send() ? "sent" : "error");
echo json_encode($response);

Answer 1

You need use proper RFC 2822 formating.
Don't use # because you don't know what is the error. If you format mails in format "user#example.com, anotheruser#example.com" it's correct and you need search problem elsewhere.
You can also see example #4 on http://php.net/manual/en/function.mail.php#example-3493 page.

Answer 2

although this is not a direct response to your issue, you could potentially save yourself trouble by using a pre-existing email sending library like either:
phpmailer
https://github.com/PHPMailer/PHPMailer
or simplesmtp
https://bitbucket.org/ghorwood/simplesmtp/