Best bet is to use a mail relay server and do your ldap or whatever lookups to your exchange box from there. GFI will do it for you, there are others too. Greg Mulholland ________________________________ From: exchangelist-bounce@xxxxxxxxxxxxx on behalf of Crockett, Gregory Sent: Sun 18/06/2006 3:25 AM To: exchangelist@xxxxxxxxxxxxx Subject: [ExchangeList] SMTP - Blocking messages where the the recipient does not exist in the GAL. Is there anyway to accomplish the above at the firewall - we are using ISA? We are receiving ton of messages with anything left of the @. Some of the recipients: jkyxpzbjzqkli@xxxxxxxxx lggxxtpghdx@xxxxxxxxx jxbhwutklun@xxxxxxxxx Is there a way to extend Recipient Filtering to the firewall? TIA greg All mail to and from this domain is scrutinized by the Scrutinizer.