The system is a MS Small Business Server. Recently installed Service Pack 2 for Windows Server 2003. In the last few days, a number of message queues (outgoing/SMTP) are failing to connect with the error described above. Event log reports:
Event Type: Warning
Event Source: MSExchangeTransport
Event Category: Connection Manager
Event ID: 4007
Message delivery to the host '18.104.22.168' failed while delivering to the remote domain 'iper.co.uk' for the following reason: The connection was dropped due to an SMTP protocol event sink.
The SMTP verb which caused the error is 'quit'. The response from the remote server is ''.
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp
0000: f3 02 04 c0 ÃƒÂƒÃ‚Â³..ÃƒÂƒÃ‚Â€
I've run smtpdiag tool on the machine and all test pass in the verbose mode.
In front of the server is a Prodigy PRO firewall from GSEC1 which is running a transparent SMTP proxy.
Anyone have any pointers?