Avoid triggering DeprecationWarnings in test_smtpd and smtpd.
diff --git a/Lib/smtpd.py b/Lib/smtpd.py
index dd83988..ca68790 100755
--- a/Lib/smtpd.py
+++ b/Lib/smtpd.py
@@ -293,10 +293,10 @@
                 else:
                     data.append(text)
             self.received_data = NEWLINE.join(data)
-            status = self.__server.process_message(self.peer,
-                                                   self.mailfrom,
-                                                   self.rcpttos,
-                                                   self.received_data)
+            status = self.smtp_server.process_message(self.peer,
+                                                      self.mailfrom,
+                                                      self.rcpttos,
+                                                      self.received_data)
             self.rcpttos = []
             self.mailfrom = None
             self.smtp_state = self.COMMAND