diff --git a/muk_web_preview_mail/controllers/main.py b/muk_web_preview_mail/controllers/main.py
index d07a2b3..8421ba5 100644
--- a/muk_web_preview_mail/controllers/main.py
+++ b/muk_web_preview_mail/controllers/main.py
@@ -47,7 +47,9 @@ class MailParserController(http.Controller):
             return werkzeug.exceptions.UnsupportedMediaType(
                 _("Unparsable message! The file has to be of type: message/rfc822"))
         else:
-            message = request.env['mail.thread'].message_parse(content.decode("latin-1").encode("utf8"), False)
+            if not attachment:
+                content = content.decode("latin-1").encode("utf8")
+            message = request.env['mail.thread'].message_parse(content, False)
             return self._make_parse_response(request.httprequest.url, message, attachment)
         
     def _set_query_parameter(self, url, param_name, param_value):