Exchange server 2003 Enterprise Edition SP2 on Windows Server 2003 SP1, all updates installed.
SMTP service stops working with above error when trying to connect to port 25 every day and sometimes twice/day since 21/11/2006. There were 2 Windows sequrity updates on 15/11/2006. We tried to uninstall them but without a result. When SMTP service is restarted the problem continues. The solution for now is to restart entire IIS - until next stop of functionality. All categories in MSExchangeTransport are set to medium logging level but there is no any error/warning event around the time the service stops working.