I'm having a problem with my newly installed exchange 07 rejecting the "mail from:<>" command with an address error. As far as i know thisbehavioris allowed by RFC. The problem is that an ISP which hosts some domains i want to communicate with uses thisbehaviorto check back with my exchange if the sending user account exists but gets interrupted before the "rcpt to:" and consequently the mailI've send never reaches therecipient. Is there a way to change this behavior in exchange 07? Any help or hints in the right direction would be very appreciated.

Is this happening on your Edge server, Hub Transport or another SMTP Relay? Your hub transport sould not be internet facing, i.e. there should be a relay between it & the general joe-public. If the connection is being terminated before the RCPT TO: then you need to check why, is there a reason given by Exchaneg or is the session simply terminated? If it is simply terminated then check your network connectivity.

Hi, Exchange 2007 can accept command mail from:<> by default, and there is no way to reconfigure it. The mail from address can be any SMTP address that you want, but some SMTP mail systems filter messages based on the MAIL FROM: address and may not permit certain IP addresses to connect or may not permit the IP address to send e-mail to the SMTP mail system if the connecting IP address does not match the domain where the SMTP mail system resides. So I suggest you disable all 3rd party software temporarily on your server and test the issue again. Regarding the error 500 Command not recognized, it can be caused by the SMTP server does not recognize what you typed because of a syntax error or an erroneous command. The solution is Check the command and type it again or verify that you are communicating directly to a Microsoft SMTP server. In your situation, the behavior is not expected to occur. Please test the issue locally, to see if mail from:<> can be accepted. If it works, you may need to contact the ISP you mentioned to get a workaround. Related KB article for your convenience: XFOR: Telnet to Port 25 to Test SMTP Communication http://support.microsoft.com/?id=153119 Hope this helps. Thanks, Elvis