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No port 25 flow. Port not open.

Posted on 2012-12-31
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Last Modified: 2013-01-21
HI,

I have a functional exchange 2003 server - all works fine but I need to make a change to have the mail.mycompany.com resolve to another ip address - on another router - which is a draytek 2820. This is on a separate phone line.

Before I change the ip address that the mail server url points to, I wanted to verify the flow of port 25 traffic through the router - so that when the change takes place, it should be a fairly seamless cut over -and the mail flows to another ipaddress/router and then to the mail server.

So I have duplicated the port settings on the 2820 and tried to telnet to the external ip on 25 -  but no connection -it wont let me. Even with both port forwarding and open port set (just to see what happens) its still bounces back. Port scans show the port is not open. Management interface shows ports defined as default but none mention 25. The ISP is the same as the other line that works ok - doesnt hesitate on telnet to 25. Cant think right now what I'm doing wrong - probably something so obvious I cant see it.. any pointers?  Thanks
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Question by:pabby0612
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Expert Comment

by:cpmcomputers
ID: 38732254
Can't help with the routing issue but thought it may help to suggest you put both ip's in your external Dns with mx records with different priorities

That way if the connection fails to your new ip (assuming it is set to the lower priority) for any reason
Mail continuity will be preserved to the old ip whilst you resolve the problem
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Expert Comment

by:_OpenSys_
ID: 38732304
Frist check if in local lan you can telnet it in port 25, if yes you ca pass to the routing.
Some ISP's block's port 25 to avoid spam storms, so if you have a dynamic ip address you may have be blocked. Buy some public IP address or talk with your IPS help-desk.

The other possibility is 2003 firewall or exchange connecting policy.
Also check's the gateway to internet if is correct.
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Author Comment

by:pabby0612
ID: 38739393
Hi, I have 5 static IP addresses from the ISP. Its the same ISP that is allowing port 25 traffic on our other line.

Cannot telnet on port 25 to the router from local LAN.

thanks
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Expert Comment

by:cpmcomputers
ID: 38739465
does the mailserver connect directly to the existing router or via a network switch

How many NIc's does it have and are they on internal or external assigned ip's?
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Author Comment

by:pabby0612
ID: 38739664
To go back to the original reason for this change - I wanted to apply an ssl cert to OWA 2003. But, we have a .net web service website in IIS that is crucial to our business that uses port ssl cert on 443. I thought that we could use 443 again for owa as long as it was on another static internal IP address. and not "all unassigned". But when we tried to apply the ssl cert, we could not. The https://mail.mycompany.com/exchange was getting certificate errors and there seemed to be some confusion/clash with the existing certificate on 443.

We could do it with a random port number like 8018 or something but that means all users need to remember this port number and manually type it in  (as far as I am aware) - I had just wanted the url to be https://mail.mycomany.com/exchange

The advice given at the time was to use a different external static ip . Hence testing smtp flow before making any changes. However, I have since thought of an additional issue that will could complicate further and it might be better to see if I can resolve the original issue first. So - 443 - any advice? Maybe should post separately.. Thanks
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Expert Comment

by:cpmcomputers
ID: 38739689
I would do a seperate post for this
its an IIS cert issue rather than tcp/ip routing

Hope you get it sorted
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Accepted Solution

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pabby0612 earned 0 total points
ID: 38786283
Hi  - Thanks for your input, however I have identified a solution to this issue which has nothing to do with the original posting.  I really appreciate the efforts of the experts. Thanks again.
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Author Closing Comment

by:pabby0612
ID: 38800571
I have identified an alternative solution which circumvents this technical problem and this question is no longer valid in the new scenario. Thank You.
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