I have Exchange Enterprise 2003 SP2 on Windows 2003. We outsource for spam filtering, virus, etc. Exchange has a “connector” to connect to “smart host” which is server of spam filtering company. Exchange also has a “Default SMTP Virtual Server” for “connector”. I also deny relaying from outside. In firewall, I configure to allow only block of IP addresses from outsourced company to SMTP with our Exchange server. Now, outsource company said telnet to our Exchange server gave the following results. telnet postoffice.ias.unu.edu 25 220 **************************************************************************************************************** quit 500 5.3.3 Unrecognized command Please note that mail flow between our Exchange server and outsourced company seems to be fine. In fact, I can’t even telnet to Exchange server from computer which is within the same subnet with Exchange server. To make another test, I put block of IP addresses from different network to firewall to allow SMTP traffic and I tried to telnet from that IP address block but telnet failed. Could you suggest that why outsourced company can telnet with result shown? Thanks. KPS

Sound like SMTP fixup protocol issue, (The Auth and Auth login commands (Extended Simple Mail Transfer Protocol [ESMTP] commands) are stripped by the firewall) which you need to turn it off on the firewall , something like this From CISCO CLI: NO FIXUP PROTOCOL SMTP 25 FIXUP protocal issues http://support.microsoft.com/kb/320027 Disbled Fixup Protocol http://www.eudora.com/techsupport/kb/2539hq.html Good luck ocd Oz Casey, Dedeal, Microsoft MVP - Exchange Server, MCITP (EMA), MCITP (EA), MCITP (SA) Visit smtp25.blogspot.com Visit Telnet25.wordpress.com This posting is provided AS-IS with no warranties or guarantees and confers no rights.

Hello, Thank you for sending the useful links and suggestion which can solve out the problem. KPS