diff --git a/lib/kolab_sync_timezone_converter.php b/lib/kolab_sync_timezone_converter.php
--- a/lib/kolab_sync_timezone_converter.php
+++ b/lib/kolab_sync_timezone_converter.php
@@ -57,6 +57,14 @@
         )
     );
 
+
+    protected $_legacyTimezones = array(
+        # This is an outdated timezone that outlook keeps sending because of an outdate timezone database on windows
+        'Lv///0kAcgBhAG4AIABTAHQAYQBuAGQAYQByAGQAIABUAGkAbQBlAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAkABAADABcAOwA7AOcDAAAAAEkAcgBhAG4AIABEAGEAeQBsAGkAZwBoAHQAIABUAGkAbQBlAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAMAAwAEAAAAAAAAAAAAxP///w==' => array(
+            'Asia/Tehran' => '+0330'
+        )
+    );
+
     /**
      * don't use the constructor. Use the singleton.
      *
@@ -140,6 +148,9 @@
         if (is_string($_offsets) && isset($this->_knownTimezones[$_offsets])) {
             $timezones = $this->_knownTimezones[$_offsets];
         }
+        elseif (is_string($_offsets) && isset($this->_legacyTimezones[$_offsets])) {
+            $timezones = $this->_legacyTimezones[$_offsets];
+        }
         else {
             if (is_string($_offsets)) {
                 // unpack timezone info to array
diff --git a/tests/timezone_converter.php b/tests/timezone_converter.php
--- a/tests/timezone_converter.php
+++ b/tests/timezone_converter.php
@@ -29,6 +29,13 @@
 
         $this->assertTrue(is_array($output));
         $this->assertTrue(isset($output['Asia/Tehran']));
+
+        # As seen in outlook
+        $converter = kolab_sync_timezone_converter::getInstance();
+        $output = $converter->getListOfTimezones('Lv///0kAcgBhAG4AIABTAHQAYQBuAGQAYQByAGQAIABUAGkAbQBlAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAkABAADABcAOwA7AOcDAAAAAEkAcgBhAG4AIABEAGEAeQBsAGkAZwBoAHQAIABUAGkAbQBlAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAMAAwAEAAAAAAAAAAAAxP///w==');
+
+        $this->assertTrue(is_array($output));
+        $this->assertTrue(isset($output['Asia/Tehran']));
     }
 
     function data_get_timezone()