Error with PHP mail(): Multiple or malformed newlines found in additional_header

None of the above answers solved this problem for me. So, I expanded my search to "mail with attachment and HTML message issues." Piecing together info from a few different posts, I came up with this. It allows for BOTH HTML email and an attachment.

My original header code:

$header = "From: ".$from_name." <".$from_mail.">\r\n";
$header .= "Reply-To: ".$replyto."\r\n";
$header .= "MIME-Version: 1.0\r\n";
$header .= "Content-Type: multipart/mixed; boundary=\"".$uid."\"\r\n";
$header .= "--".$uid."\r\n";
$header .= "Content-Type: text/html; charset=ISO-8859-1\r\n";
$header .= "Content-Transfer-Encoding: 8bit\r\n";
$header .= $body."\r\n";
$header .= "--".$uid."\r\n";
$header .= "Content-Type: application/pdf; name=\"".$filename."\"\r\n"; 
$header .= "Content-Transfer-Encoding: base64\r\n";
$header .= "Content-Disposition: attachment; filename=\"".$filename."\"\r\n";
$header .= $content."\r\n";
$header .= "--".$uid."--";

if (mail($mail_to, $subject, "", $header))
{
    return "mail_success";
}
else
{
    return "mail_error";
}

My new code (complete): Note that $body is the HTML that is being assembled by a different function.

$file = $path.$filename;
$file_size = filesize($file);
$handle = fopen($file, "r");
$content = fread($handle, $file_size);
fclose($handle);

$content = chunk_split(base64_encode($content));
$uid = md5(uniqid(time()));
$name = basename($file);

$eol = PHP_EOL;

// Basic headers
$header = "From: ".$from_name." <".$from_mail.">".$eol;
$header .= "Reply-To: ".$replyto.$eol;
$header .= "MIME-Version: 1.0\r\n";
$header .= "Content-Type: multipart/mixed; boundary=\"".$uid."\"";

// Put everything else in $message
$message = "--".$uid.$eol;
$message .= "Content-Type: text/html; charset=ISO-8859-1".$eol;
$message .= "Content-Transfer-Encoding: 8bit".$eol.$eol;
$message .= $body.$eol;
$message .= "--".$uid.$eol;
$message .= "Content-Type: application/pdf; name=\"".$filename."\"".$eol;
$message .= "Content-Transfer-Encoding: base64".$eol;
$message .= "Content-Disposition: attachment; filename=\"".$filename."\"".$eol;
$message .= $content.$eol;
$message .= "--".$uid."--";

if (mail($mail_to, $subject, $message, $header))
{
    return "mail_success";
}
else
{
    return "mail_error";
}

Two key changes here. (1) removed all the multi-part stuff from the headers into $message. (2) removed all the "\r\n" stuff and added $eol = PHP_EOL; to the code.

Together, these changes allowed me to once again send HTML email with attachments.

Had just the similar problem.
It came out of the blue. No PHP Code was changed.

What was changed: PHP was upgraded 5.5.25-1 to 5.5.26.

A security risk in PHP mail() function has been fixed and extra newlines in additional_headers are allowed no more. Because extra newlines mean: now starts the email message (and we surely don't want somebody to inject some newlines through headers followed by an evil message).

What previously have worked fine, e.g. just having extra newlines after headers or even passing the whole message to additional_headers, will function no more.

Solution:

• Sanitize your headers. No multiple newlines in additional_headers argument. These count as "multiple or malformed newlines": \r\r, \r\0, \r\n\r\n, \n\n, \n\0.
• Use additional_headers for headers only. Email message (multipart or not, with ir without attachments, etc) belongs in message argument, not in headers.

PHP Security Bug report: https://bugs.php.net/bug.php?id=68776
C Code diff how its fixed: http://git.php.net/?p=php-src.git;a=blobdiff;f=ext/standard/mail.c;h=448013a472a3466245e64b1cb37a9d1b0f7c007e;hp=1ebc8fecb7ef4c266a341cdc701f0686d6482242;hb=9d168b863e007c4e15ebe4d2eecabdf8b0582e30;hpb=eee8b6c33fc968ef8c496db8fb54e8c9d9d5a8f9