Problem with mail headers

[ReekenX]

Hi everyone. I have my own PHP framework. 3 months of hard work. I have done 7 websites with framework, but two days ago, I have found strange bug.

I am using this function:

/**
 * Send mail
 *
 * @param  string $To          Send email to
 * @param  string $From        Send from
 * @param  string $Subject     Email subject
 * @param  string $Body        Email body
 * @param  string $Encoding    Encoding to use
 * @param  string $Type        Email type (html or plain)
 * @return void
 * @access public
 */
if (!function_exists("send_mail"))
{
    function send_mail($To, $From, $Subject, $Body, $Encoding = "iso-8859-1", $TYPE = "plain")
    {
        $Headers  = "From: " . $From . "\r\n";
        $Headers .= "Reply-To: " . $From . "\r\n";
        $Headers .= "Return-Path: " . $From . "\r\n";
        $Headers .= "Content-Type: text/" . $TYPE . "; charset=" . $Encoding . "\r\n";
        $Headers .= "X-mailer: ReekenX WForce Framework\r\n";
        mail($To, $Subject, $Body, $Headers);       
    }
} 

The solution I have found is to replace \r\n with only \n. In 6 servers, my mail sending was correct, but in one, mail headers was seen in message body. Like:

From: sender@sender.com
Reply-to: sender@sender.com
(other headers seen here)

Message text

Can anybody explain why email sending with \r\n is bad, and with \n is right?

Sorry for my poor english

[Xav]

\r is a carriage return (ASCII char 13), \n is a new line (ASCII char 10). Sometimes one or the other is required, sometimes both. It depends on the language used. I dunno why it isn't working ATM.

[John]

According to the RFC2822, all mail headers should be terminated with a CRLF (carriage return line-feed), so it is not an issue with your code. I could be wrong, but I have read some linux servers replace a LF with a CRLF automatically, thus creating a double CR which results CRCRLF [\r\r\n] and thus is invalid.

[TkTech]

PHP themselves recommend \r\n...however, they also state:

Note: If messages are not received, try using a LF (\n) only. Some poor quality Unix mail transfer agents replace LF by CRLF automatically (which leads to doubling CR if CRLF is used). This should be a last resort, as it does not comply with » RFC 2822

[ReekenX]

Many thanks to everyone!