Add a comment to the X-Priority header (Highest,Normal,Lowest).

This is common in other clients, and some SpamAssassin rule triggers
on the absence of such.

ChangeLog

@@ -18,7 +18,8 @@ Version 1.5.1 -- CVS
   - Fix non selectable inbox.
   - Add src/configtest.php script which checks for common errors in the config.
   - Improve display of some unparsable/absent dates (#891354).
-  
+  - Add comment (Highest,Normal,Lowest) to X-Priority header.
+    Some SpamAssassin rule triggers on the absence of such a comment.
 
 Version 1.5.0
 --------------------

class/deliver/Deliver.class.php

@@ -459,13 +459,17 @@ class Deliver {
             $header[] = 'Disposition-Notification-To: '.$dnt. $rn;
         }
         if ($rfc822_header->priority) {
-            $prio = $rfc822_header->priority;
-            $header[] = 'X-Priority: '. $prio. $rn;
-            switch($prio)
+            switch($rfc822_header->priority)
             {
-            case 1: $header[] = 'Importance: High'. $rn; break;
-            case 3: $header[] = 'Importance: Normal'. $rn; break;
-            case 5: $header[] = 'Importance: Low'. $rn; break;
+            case 1:
+	    	$header[] = 'X-Priority: 1 (Highest)'.$rn;
+	    	$header[] = 'Importance: High'. $rn; break;
+            case 3:
+	    	$header[] = 'X-Priority: 3 (Normal)'.$rn;
+	    	$header[] = 'Importance: Normal'. $rn; break;
+            case 5:
+	    	$header[] = 'X-Priority: 5 (Lowest)'.$rn;
+	    	$header[] = 'Importance: Low'. $rn; break;
             default: break;
             }
         }