Most MTA/MUA’s insert a lot of extra headers; however, here is sort of the bare minimum you can expect.
From: Reply-To: To: Subject: Date: date("r"); MIME-Version: Content-Type:
If you using HTML, then you should probably be using multipart messages–but it’s not strictly necessary.
Here is a snippet of code that shows how multi-part mime headers can be assembled without the help of a mailer class.
<? $mime_boundary=md5(time()); $headers .= 'From: My Email <me@company.com>' . "\n"; $headers .= 'MIME-Version: 1.0'. "\n"; $headers .= "Content-Type: multipart/mixed; boundary=\"".$mime_boundary."\"". "\n"; $msg .= "--".$mime_boundary. "\n"; $msg .= "Content-Type: text/plain; charset=iso-8859-1". "\n"; $msg .= "Content-Transfer-Encoding: 7bit". "\n\n"; $msg .= $textmessage . "\n\n"; $msg .= "--".$mime_boundary. "\n"; $msg .= "Content-Type: application/pdf; name=\"".$filename."\"". "\n"; $msg .= "Content-Transfer-Encoding: base64". "\n"; $msg .= "Content-Disposition: attachment; filename=\"".$filename."\"". "\n\n"; $msg .= chunk_split(base64_encode($doc)) . "\n\n"; $msg .= "--".$mime_boundary."--". "\n\n"; ?>