Looks like at least some TNEF files don't contain the VERSION data.

It's legacy, and can be set to anything, but it's supposed to
still be present. Either way, only parse it if we find the VERSION
attribute instead of assuming it's there.

framework/Compress/lib/Horde/Compress/Tnef.php

@@ -245,11 +245,6 @@ public function decompress($data, array $params = array())
                 $this->_geti($data, 16))
             );
 
-            // Version
-            $this->_geti($data, 8); // LVL_MESSAGE
-            $this->_getx($data, $this->_geti($data, 32)); //AVERSION
-            $this->_geti($data, 16); //checksum
-
             $out = array();
             $this->_msgInfo = new Horde_Compress_Tnef_MessageData($this->_logger);
             while (strlen($data) > 0) {
@@ -626,6 +621,11 @@ protected function _decodeMessageProperty(&$data)
             $this->_geti($data, $this->_geti($data, 32));
             $this->_geti($data, 16); //checksum
             break;
+        case self::AVERSION:
+            // Version
+            $this->_getx($data, $this->_geti($data, 32)); //AVERSION
+            $this->_geti($data, 16); //checksum
+            break;
         case self::AFROM:
         case self::ASENTFOR:
             $display_name = $this->_getx($data, $this->_geti($data, 16));