diff -u --recursive movespam-vanilla/config.inc.php.dist movespam/config.inc.php.dist
--- movespam-vanilla/config.inc.php.dist	2014-10-18 09:38:13.193908022 -0400
+++ movespam/config.inc.php.dist	2014-10-18 09:38:20.699924299 -0400
@@ -1,7 +1,10 @@
 <?php
 
-// If this string is at the beginning of the subject, the message will be moved to the junk folder.
-$rcmail_config['movespam_subject'] = '***SPAM***';
+// Name of the header to inspect.
+$rcmail_config['movespam_key'] = 'subject';
+
+// If this string is at the beginning of the header, the message will be moved to the junk folder.
+$rcmail_config['movespam_value'] = '***SPAM***';
 
 // True to move all spam. False to move only new (unread) spam.
 $rcmail_config['movespam_seen'] = false;
diff -u --recursive movespam-vanilla/movespam.php movespam/movespam.php
--- movespam-vanilla/movespam.php	2014-11-10 22:54:05.668094687 -0500
+++ movespam/movespam.php	2014-11-10 22:53:24.001285066 -0500
@@ -3,7 +3,7 @@
 /**
  * MoveSpam
  *
- * Automatically move spam messages to the junk folder based on the subject line.
+ * Automatically move spam messages to the junk folder based on a header line.
  *
  * @version 1.0
  * @author Ythan
@@ -13,20 +13,33 @@
 	public $task = 'mail';
 	private $open_mbox = 'INBOX';
 	private $spam_mbox = 'JUNK';
-	private $spam_text = '***SPAM***';
+	private $spam_key  = 'subject';
+	private $spam_value= '***SPAM***';
 	private $move_seen = false;
 
 	function init()
 	{
 		$rcmail = rcmail::get_instance();
 		$this->load_config();
-		$this->spam_mbox = $rcmail->config->get('junk_mbox', null);
-		$this->spam_text = $rcmail->config->get('movespam_subject', null);
-		$this->move_seen = $rcmail->config->get('movespam_seen', null);
+		$this->spam_mbox  = $rcmail->config->get('junk_mbox', null);
+		$this->spam_key   = $rcmail->config->get('movespam_key', null);
+		$this->spam_value = $rcmail->config->get('movespam_value', null);
+		$this->move_seen  = $rcmail->config->get('movespam_seen', null);
 		if($rcmail->task == 'mail') {
+			$this->add_hook('storage_init', array($this, 'fetch_headers'));
 			$this->add_hook('messages_list', array($this, 'check_headers'));
 		}
 	}
+
+	function fetch_headers($fields)
+	{
+		$key = strtolower($this->spam_key);
+		if(!stripos($fields['fetch_headers'], $key)){
+			array_push($fields, $key);
+			$fields['fetch_headers'] = trim($fields['fetch_headers'] . ' ' . strtoupper($key));
+		}
+		return $fields;
+	}
 	
 	function check_headers($mlist)
 	{
@@ -35,9 +48,9 @@
 		$this->open_mbox = $imap->get_folder();
 		
 		if(is_array($mlist['messages']) && $this->open_mbox != $this->spam_mbox){
-			
 			foreach($mlist['messages'] as $message){				
-				if (strpos($message->subject, $this->spam_text) === 0){
+				$value = $message->get($this->spam_key);
+				if (strpos($value, $this->spam_value) === 0){
 					if (!$message->seen || $this->move_seen){
 						$spam_uids[] = $message->uid;
 					}
@@ -47,7 +60,7 @@
 			if (count($spam_uids)){
 				$spam_uids_str = implode(',', $spam_uids);
 				$imap->move_message($spam_uids_str, $this->spam_mbox, $this->open_mbox);				
-				$unseen_count = $imap->messagecount($this->spam_mbox, 'UNSEEN');
+				$unseen_count = $imap->count($this->spam_mbox, 'UNSEEN');
 				$rcmail->output->command('set_unread_count', $this->spam_mbox, $unseen_count, false);
 				$this->api->output->command('list_mailbox');
 				$this->api->output->send();