Two minor changes:

- In SMTP.send, there is a check for self.sock, which may  not exist if there has been no attempt to connect.  This patch adds a check for hasattr(self, 'sock') so that such an attempt to call send() will raise the more helpful SMTPServerDisconnected instead of an AttributeError.

- The docstring for SMTP.expn is a copy of that of the verify method.  This patch changes it to something more appropriate.