I believe you need to change the size of the NOOP command from a maximum length of 6 to 1024. That should fix the problem. Open ISA MMC open Application filters right click to properties. Properties on NOOP. HTH Joe -----Original Message----- From: Lanny [mailto:Lannyshen@xxxxxxxxxxxxxxx] Sent: Monday, November 12, 2001 2:06 AM To: [ISAserver.org Discussion List] Subject: [isalist] RE: Problem with SMTP Relay on ISA + Exchange Server 2K http://www.ISAserver.org I have the same trouble,but if you disable SMTP Filter in ISA,and select 'Only the list below'&needn't add any option&select below pane in Exchange, users can authenticate to send mail from outside of system;but enable SMTP Filter in ISA,the authentication can't be authenticate by ISA,because the SMTP command is unknow.I need answer too. ------------------------------------------------------ You are currently subscribed to this ISAserver.org Discussion List as: joe@xxxxxxxxxxxxxxx To unsubscribe send a blank email to $subst('Email.Unsub')