in Mime_Helper::getCharacterSet() if the email cis multipart/mixed and contains
only one subpart, take the charset from that first part, rather from primary
part.

--- eventum-20060725/include/class.mime_helper.php	2006-07-26 11:29:55.240578707 +0300
+++ include/class.mime_helper.php	2006-07-26 14:20:18.000000000 +0300
@@ -67,7 +67,13 @@
             return false;
         }
 
-        $content_type = @$structure->headers['content-type'];
+        if ($structure->ctype_primary == 'multipart' and $structure->ctype_secondary == 'mixed'
+            and count($structure->parts) == 1) {
+            $content_type = $structure->parts[0]->headers['content-type'];
+        } else {
+            $content_type = @$structure->headers['content-type'];
+        }
+
         if (preg_match('/charset\s*=\s*(["\'])?([-\w\d]+)(\1)?;?/i', $content_type, $matches)) {
             return $matches[2];
         }