Oh brother. You do not know what you are doing, do you? 1. If you are using the included Internet Connection Firewall that comes with Windows XP and Windows 2003 server, you do not understand. You CAN NOT USE THAT! That is a basic basic basic dumb firewall that is only a stop gap measure. 2. Generally speaking, (unless you purchased the cheap version,) ISA 2000 is included with Small Buisness Server 2003. 3. You are using a Linksys (what, DSL,) basic router that is not a firewall. Some one needs to take some time and think about security. Operating an Exchange e-mail server, or any flavor of e-mail server on the Internet, REQUIRES dedication and understanding of the ramifications of doing so. This includes taking basic standard security steps at the very least. For the Exchange server on SBS, disable the ICF and configure ISA server and publish the Exchange server properly. On the other client behind the Linksys, 86 the Linksys router, break down and get a SonicWall TZ170 and configure the SMTP and POP3 protocols. John Tolmachoff Engineer/Consultant/Owner eServices For You -----Original Message----- From: Mark M. Friedman [mailto:mark@xxxxxxxxxxxxxxxx] Sent: Wednesday, April 07, 2004 1:23 AM To: [ExchangeList] Subject: [exchangelist] RE: Error from yahoo: wasn't able to establish an SMTP connection. (#4.4.1) http://www.MSExchange.org/ One is Win2k3 small biz srvr (Not ISA) built in firewall and the other client has a basic linksys setup. _____