PHP mail function how to set sender mail id based on if condition?

I am using magento for sending mail with condition,

My code:

<?php
class Gta_MerchantNotification_Model_Observer {
    public function merchantremainder($Observer) {
       $order = $Observer->getEvent()->getOrder();
       $order_details = $order->getAllVisibleItems();

       $itemData = array();
       foreach ($order_details as $list) {
          $incrementid = $order->getIncrementId();
          $sku = $list->getsku();
          $name = $list->getName();
          $price = $list->getPrice();
          $Qty = $list->getQtyOrdered();
          $extra = $order->getIncrementId();
          $message = 

          "
          <tr>
          <!-- <td>$incrementid</td> -->
          <td>$sku</td>
          <td>$name</td>
          <td>$price</td>
          <td>$Qty</td>
          </tr>";

          $itemData[$list->getId()] = $message;

      }

      $finalMessage =  "
      <p>Order Id : $incrementid</p>
      <table border='1'>

      <tr>
      <!-- <th>Id</th> -->
      <th>Sku</th>
      <th>Product name</th>
      <th>Price</th>
      <th>Qty Ordered</th>
      </tr>";
      if (!empty($itemData)) {
          foreach ($itemData as $data) {
             $finalMessage .= $data;
         }

         $finalMessage .= "</table>";
         $this->sendMail($finalMessage);
     }

 }

 public function sendMail($message) {
   $body ="$message";
   $emailTemplate = Mage::getModel('core/email');
   $emailTemplate->setFromName('abc');
   $emailTemplate->setBody($body);
   $emailTemplate->setSubject("Custom Email from observer");
   $emailTemplate->setType('html');
   $emailTemplate->setToEmail('abc@gmail.com');
   $emailTemplate->send();

}
}

?>

Output :

https://snipboard.io/encLQH.jpg

If order placed mail send to abc@gmail.com.
How to set email sender based on SKU $sku from order.

I want :

1) If SKU starts with 2, email should go to the mail id abc@gmail.com,
screenshot :

https://snipboard.io/2aiBze.jpg

2) If SKU starts with 3, email should go to the mail id xyz@gmail.com,
screenshot :

https://snipboard.io/tmWfEx.jpg

3) If SKU starts with 4, email should go to the mail id qwe@gmail.com,
screenshot :

https://snipboard.io/M5dGIn.jpg

FYI - If an order contains 10 items email should go separately based on SKU. But an order id the same must include all the emails.