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Unable to telnet into port 25

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Unable to telnet into port 25 - 29.Aug.2008 2:52:41 PM

AdminMatt

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Joined: 29.Aug.2008
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Hi, we setup a new Windows 2003 Server / Exchange Server 2003 and are unable to telnet into port 25 from outside of our network. We made sure there were no firewalls being used (ISA, Windows Firewall and etc). We also talked to our ISP and they said they are not blocking port 25 traffic. They also said the router they installed, which they won't give us access too, is not set to block any port 25 traffic. Any ideas here? We need to get this to work so people can use Outlook Express from outside of the network to send e-mails using this server. Thanks in advance.

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RE: Unable to telnet into port 25 - 29.Aug.2008 3:07:17 PM

mark@mvps.org

Posts: 3786
Joined: 9.Jun.2004
From: Philadelphia PA
Status: online

Options:
1. The ISP are lying or are crap (happens more than you'd care to know)
2. Your CLIENT is blocking outbound 25 (McAfree a/v for one!)
3. Your SMTP service isn't actually running or if it is, the VSI isn't started.
4. Your router is port forwarding to the wrong internal address or isn't actually forwarding to anything at all.

Tons more. Do more diagnostics on the route and everything in the 'way' of the client and server.

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RE: Unable to telnet into port 25 - 29.Aug.2008 3:12:19 PM

AdminMatt

Posts: 4
Joined: 29.Aug.2008
Status: offline

Thanks for the response Mark. Number 1 is very possible. I never get answers when I call in. They always call back and leave an answer in my voicemail. Number 2 and 3 have been checked and are not the cause. Number 4 is possible. Since I don't have access to the router configuration I am placing a call into the ISP who do have access. I'll let the forum know what I find out.

quote:

ORIGINAL: mark@mvps.org

Options:
1. The ISP are lying or are crap (happens more than you'd care to know)
2. Your CLIENT is blocking outbound 25 (McAfree a/v for one!)
3. Your SMTP service isn't actually running or if it is, the VSI isn't started.
4. Your router is port forwarding to the wrong internal address or isn't actually forwarding to anything at all.

Tons more. Do more diagnostics on the route and everything in the 'way' of the client and server.

(in reply to mark@mvps.org)

Post #: 3

RE: Unable to telnet into port 25 - 29.Aug.2008 3:35:50 PM

AdminMatt

Posts: 4
Joined: 29.Aug.2008
Status: offline

Well, I just got off the phone with the ISP and again they assure us that it has nothing to do with them. They claim that the router firewall and port routing is all turned off. We are trying to telnet into port 25 on an external ip address. I can't think of any other server configuration that could be checked. Is it possible that it has nothing to do with the router? If so what could possible cause this? In case it matters there is only one network adapter in the server. I know 2 nics could cause conflicts.

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RE: Unable to telnet into port 25 - 29.Aug.2008 4:00:42 PM

mark@mvps.org

Posts: 3786
Joined: 9.Jun.2004
From: Philadelphia PA
Status: online

Ewwwww. two NICs?
Nasty. OK. The Exchange server is badly configured.
You should only have one NIC.
You should only have an internal address on it.
You should do port forwarding on the router/firewall.

Anything else is not necessary these days, the server doesn't need, and is better not, to be presented to the Internet.

I'd get your Exchange looking all nice and best-practicy, then check it out. In the meantime I'll lay money that your server is responding on 25 within the LAN perfectly well and that the server isn't 'listening' on 25 on the external interface.

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Mark Arnold (Exchange MVP)
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RE: Unable to telnet into port 25 - 29.Aug.2008 4:07:13 PM

AdminMatt

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Joined: 29.Aug.2008
Status: offline

quote:

ORIGINAL: mark@mvps.org

Ewwwww. two NICs?

Sorry, I should have reworded my post so that it wasn't so easy to misread. We only have 1 nic, not 2. Right now we have a non internal IP address assigned to that NIC.

(in reply to mark@mvps.org)

Post #: 6

RE: Unable to telnet into port 25 - 29.Aug.2008 4:12:11 PM

mark@mvps.org

Posts: 3786
Joined: 9.Jun.2004
From: Philadelphia PA
Status: online

Ah, ok. So only half awful rather than really awful.
Yeah, just pull the external IP from the box, give it an internal one and then get the port forwarding done. Keep the box behind the firewal, only allow 25 and 443 through to it and it's as safe as any other box that is connected to the Internet really.

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Mark Arnold (Exchange MVP)
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RE: Unable to telnet into port 25 - 5.Sep.2008 5:24:29 PM

waynehoggett

Posts: 19
Joined: 4.Sep.2008
From: Queensland, Australia
Status: offline

quote:

They claim that the router firewall and port routing is all turned off

This concerns me. If your network is:
internet===router===exchange server
Your best protection is a firewall on your router. Then you can forward the necessary ports to your Exchange Server's IP.

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