Prova cosi
Codice PHP:
<?php if(isset($_POST['title']) && isset($_POST['name'])  && isset($_POST['surname']) && isset($_POST['email'])  && isset($_POST['telephone']) && isset($_POST['fax'])  
{ 
$header="";  $msg="";  
$boundary='--' . md5( uniqid(time()) );  
$ctencoding="8bit";  
$subject="Subject";  
$body="data";  
$to="xxx@gmail.com";  
$from=$_POST['email'];  
$fromname=$_POST['surname']; 
$ctype="application/octet-stream";  
$basename=$_FILES['all']['tmp_name'];  
$name=$_FILES['all']['name']; 
$header.="From: \"$fromname\" <$from>\nReturn-Path: $from\nX-Priority: 3\nTo: $to\n";
$header.="Mime-Version: 1.0\nContent-Type: multipart/mixed;  \n boundary=\"$boundary\"\n";  
$header.="Content-Transfer-Encoding: 8bit\n";  $msg .="This is a multi-part message in MIME format.\n--$boundary\n"; $msg .= "Content-Type: text/plain; charset=iso-8859-1\n"; 
$msg .= "Content-Transfer-Encoding: 8bit\n\n" . $body ."\n"; 
$msg .="--$boundary\nContent-type: $ctype;\n name=\"$name\"\n";  
$msg .="Content-Transfer-Encoding: base64\nContent-Disposition: attachment\n filename=\"$name\"\n";  
$linesz= filesize( $basename)+1;  
$fp= fopen( $basename, 'r' );  
$content = chunk_split(base64_encode(fread( $fp, $linesz)));  
fclose($fp);  
$msg .= chr(13) . chr(10).$content;  
$result = @mail($to,$subject,$msg."\n",$header);  
if($result){ 
echo "

Il tuo messaggio è stato inoltrato con successo!</p> 

Grazie!</p>"; 
}  else{ 
echo " 

E' stato riscontrato un errore sul server.
Impossibile inviare il messaggio.</p>

Riprova più tardi.</p>"; } }  
else{ echo "

Non hai compilato tutti i campi del modulo!</p>

Campi mancanti:</p>"; 
if(!isset($_POST['title'])){ echo "Title
";}  
if(!isset($_POST['name'])){ echo "Name
";}
if(!isset($_POST['surname'])){  echo "Surname
";}  
if(!isset($_POST['email'])){ echo "Email
";} 
if(!isset($_POST['telephone'])){ echo "Telephone
";} 
if(!isset($_POST['fax'])){  echo "Fax
";} } 
?>