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Connection from Linux Server by telnet connection closed by foreign host

Posted on 2008-06-12
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Last Modified: 2013-12-18
We want to send e-mail from a Linux server through an Exchange server so we don't have to add also users at the Linux system and have 2 mailservers.

However if we want to start an telnet session from a linux we get the following error:
connection closed by foreign host
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If we do a telnet from an Windows 2000 server we get a good reply from the Mailserver and can create helo domain.nl etc

thanks

Casper Lammertink
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Question by:clammertink
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LVL 16

Expert Comment

by:robrandon
ID: 21768426
Make sure you are telnetting on port 25 from the linux box.
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Author Comment

by:clammertink
ID: 21768451
we did that we did:

telnet 192.9.101.3 25
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Expert Comment

by:robrandon
ID: 21768521
Can the mail server do a reverse lookup on the linux box's IP?
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Author Comment

by:clammertink
ID: 21768671
? it replies on a ping... or unc path
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Expert Comment

by:robrandon
ID: 21768714
I think in some instances, it will try to resolve the IP back to the linux boxes name.  If you run the following command on the mail server, does it return the name of the Linux box:

NSLOOKUP <ip of linux box>

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Author Comment

by:clammertink
ID: 21768818
it gives an reply with the linux server name
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Expert Comment

by:robrandon
ID: 21768976
Check out the properties of the SMTP virtual server and see if the list is restricted to certain IP's.  If it is, confirm the IP of your linux box is in there.

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Author Comment

by:clammertink
ID: 21769708
Checked that on the relay button i added the linux box
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Author Comment

by:clammertink
ID: 21770009
sorry i meant did that aldready so that cant be the problem
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Expert Comment

by:robrandon
ID: 21770384
Is there any type of network security in place that can be doing it like an IDS?

I don't recall if you need to restart a service or not for that change to take effect.
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Author Comment

by:clammertink
ID: 21770548
IDS can't block it because both servers are running on the inside.

Services of smtp where already restarted
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LVL 16

Expert Comment

by:robrandon
ID: 21771823
Can your switches be doing something?

Something is dropping that connection.  If it's not the SMTP Virtual server, or something else on the server, then it has to be something on the network.

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Author Comment

by:clammertink
ID: 21777015
Its so strange, because from other (windows) stations which are not in the domain I can make a telnet to the server
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Expert Comment

by:robrandon
ID: 21777702
Is it possible to take the Linux box offline for a few minutes, set one of the windows boxes to the same IP as the Linux box, connect it to the network in the same fashion, and then try to telnet?  That would eliminate any type of networking issue.

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Author Comment

by:clammertink
ID: 21777727
that is difficult as it is an ecommerce server...
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Author Comment

by:clammertink
ID: 21788826
could we try something else?
According to me it can not be a ip that's been blocked...
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Expert Comment

by:robrandon
ID: 21792868
How soon after initiating the connection does it close?  Can you provide the exact output from the connection?

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Author Comment

by:clammertink
ID: 21793506
almost directly
connection closed by foreign host
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LVL 16

Expert Comment

by:robrandon
ID: 21793656
So you don't even get to enter anything at the prompt?  Do you get a hello message or anything?
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Expert Comment

by:robrandon
ID: 21793719
Go to the properties of the SMTP Virtual Server and click on the Access Tab.  Check the authentication settings there.
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Author Comment

by:clammertink
ID: 21793828
on the linux i dont receive the helo or name of exchange server message
The following  items are marked under that tab:

Anonymous access
Basic authentication
Integrated Windows Authentiacation
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Author Comment

by:clammertink
ID: 21801153
any ideas
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LVL 16

Expert Comment

by:robrandon
ID: 21801754
I don't think the connection is even opening, even though it says it was "closed" by foreign host.

I was wondering if it was a security setting that was stopping it, but with anonymous access enabled, it should be ok.  Anything else you can find in the access tab that would prevent/allow your linux computer to telnet in?

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Author Comment

by:clammertink
ID: 21801811
nope
can it also be a problem in the linux box?
At the customer side we are controlling the windows enviroment, gateway protection, firewall, but not the linux server
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Assisted Solution

by:robrandon
robrandon earned 750 total points
ID: 21801928
I don't know much about linux, but I would imagine telnet is telnet.  Can the linux box telnet to other systems?
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Author Comment

by:clammertink
ID: 21802029
that i didn't ask. But like i told in an post earlier, we can telnet from another window box that is even outside the domain(of course in the same subnet)
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Author Comment

by:clammertink
ID: 22132408
the problem was the subnet mask on the linux server!
We dont control that server on the customerside... :-(
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Accepted Solution

by:
robrandon earned 750 total points
ID: 22137037
Interesting.

Guess everything is working now.  You can probably request to get the question closed with points refunded.  No objection here.

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