better still you can:

<a href="mailto:Whomever<whomever@whereever.com>?Subject=Hello%20World">whomever@whereever.com</a>

however in PHP I hide my email addresses in a script to keep the spammers at bay so I'd have:

<a href="mailto.php?to=Whomever&subject=Hello%20World">Whomever</a>

and the script has

<? 
$to = $HTTP_GET_VARS["to"]; 
/* 
Configure the variables and case options 
*/ 
$domain = "whereever.com"; 

switch ($to) { 
    case "sales":
      $addr_info = "Whomevers Sales";
      break;

    case "support":
      $addr_info = "Whomevers ";
      break;

    case "webmaster": 
      $addr_info = "Whomevers Webmaster"; 
      break; 
    case "nzsales":
      $addr_info = "NZ Sales";
      break;
   case "refunds":
     $addr_info = "Refund Request" ;
     break;
   default: 
     $addr_info = "For: ". $to; 
     $to = "webmaster"; 
} 
if (!empty($subject)) $subject = "?Subject=".$subject;
/* send the mail header */ 
header ("Location: mailto:$addr_info <$to@$domain>".$subject); 
?>

Shouldn't be too hard to convert this.