diff -up squirrelmail-1.4.13/src/view_text.php.BAD squirrelmail-1.4.13/src/view_text.php
--- squirrelmail-1.4.13/src/view_text.php.BAD	2008-09-05 12:22:02.000000000 -0400
+++ squirrelmail-1.4.13/src/view_text.php	2008-09-05 12:23:20.000000000 -0400
@@ -84,7 +84,17 @@ if ($type1 == 'html' || (isset($override
     $body = magicHTML( $body, $passed_id, $message, $mailbox);
 } else {
     $ishtml = FALSE;
-    translateText($body, $wrap_at, $charset);
+    if($squirrelmail_language != 'ja_JP'){
+        translateText($body, $wrap_at, $charset);
+    } else {
+        if($encoding == 'base64' || $encoding == 'quoted-printable' ||
+          $encoding == 'quoted_printable'){
+           translateText($body, $wrap_at, $default_charset);
+        } else {
+            // it may never call here.
+            translateText($body, $wrap_at, $charset);
+        }
+    }
 }
 
 displayPageHeader($color, 'None');