Don't listen to Steve. He's on crack. I'm assuming you're servers are SNAT clients (int ISA nic is their default gateway) since you are publishing... you should be able to telnet to 25 on your server's external published address just fine as long as your rules allow that. I just telnet'ed from my Exchange box itself to its externally published address and it worked just fine. What do your ISA logs say? t From: isalist-bounce@xxxxxxxxxxxxx [mailto:isalist-bounce@xxxxxxxxxxxxx] On Behalf Of Paul T. Laudenslager Sent: Wednesday, December 02, 2009 4:33 PM To: isalist@xxxxxxxxxxxxx Subject: [isalist] Re: SMTP - internal to localhost issue.. Okay... Hmm... Let's say I have a bunch of customers on ServerA and a different bunch on ServerB. If customers on ServerA send customers on ServerB an email, the ServerA server resolves the IP address to the "external" or "public" IP, not the internal/local IP. I don't want to have to have maintain an entire DNS to resolve hundreds of domain names internally. I thought I had this configuration working several times before... maybe I'm wrong. One way that does work is to implement a mail relay server outside the firewall. However, that means all internal smtp traffic from one mail server to another has to go outside the firewall. There just seems something wrong with that. Me wanna worky! :) -paul ________________________________ From: isalist-bounce@xxxxxxxxxxxxx [isalist-bounce@xxxxxxxxxxxxx] On Behalf Of Steve Moffat [Steve@xxxxxxxxxx] Sent: Wednesday, December 02, 2009 7:14 PM To: isalist@xxxxxxxxxxxxx Subject: [isalist] Re: SMTP - internal to localhost issue.. Don't try to do that through ISA...no worky.... From: isalist-bounce@xxxxxxxxxxxxx [mailto:isalist-bounce@xxxxxxxxxxxxx] On Behalf Of Paul T. Laudenslager Sent: Wednesday, December 02, 2009 8:11 PM To: isalist@xxxxxxxxxxxxx Subject: [isalist] SMTP - internal to localhost issue.. Okay, I'm missing something simple here but have yet to figure it out. 1. I published (2) internal SMTP boxes to outside "live" IP addresses. I can access these internal servers on port 25 just fine on thier 'public' ips. 2. I can telnet to the SMTP port of each other's private IP address. (ie. 172.16.x.x to 172.16.x.x) Problem ====== When I try and telnet from one SMTP server to the published "public" IP of the other SMTP server, the connection is denied. I've created a rule to allow internal network to localhost network for port 25 but it is still failing. Any suggestions on what to look for next? Thanks in advance for your kind suggestions! :) -paul ________________________________ This email is confidential and should only be read by the intended recipient. ________________________________ This email is confidential and should only be read by the intended recipient.