This is an SMTP protocol log for virtual server ID 1, connection #1640. The client at "xxx.xxx.xxx.xxx." sent a "xexch50" command, and the SMTP server responded with "504 Need to authenticate first." The full command sent was "xexch50 2256 2". This will probably cause the connection to fail.
I've looked at the MS link, and have tried everything suggested; including setting the NIC manually rather than automatically. All the patches are up to date, and mail seems to be working fine. However I cannot use the cmdprmt telnet test even within the LAN. The only machine it works from is the server itself. The number of servers trying to connect is limited that I seem to get the error on. It's making me nervous though.
This is an SMTP protocol log for virtual server ID 1, connection #1503. The client at "220.127.116.11" sent a "rcpt" command, and the SMTP server responded with "550 5.7.1 Unable to relay for firstname.lastname@example.org." The full command sent was "rcpt TO: email@example.com." This will probably cause the connection to fail.
I interpret this as an attempt to relay mail thru our server. The SMTP log seems to indicate that the connection simply drops. I've tried to simply get rid of the error by turning the MSExhangeTransport logging level to minimum but I 'm still getting them.
The remote host is trying to using the XEXCH50 ESMTP verb which requires authentication. If you need to allow that, I'd recommend you setup a separate SMTP virtual server for the partner (at each end) and configure it to authenticate.