Unable to connect to port 25 except from localhost

Posted on 2006-12-01
Last Modified: 2012-05-05
Hi any help on this would really be appreciated.

We recently took on IT support for a new customer who has a small busines server 2003 which the previous IT company had left partially installed. We continued the installation rather than reinstalling completly, which I now hope we can now avoid doing.

Almost everything is fine with the exception of port 25 connetivity. In a nut shell telnet to port 25 only works from the server itself on or the local IP address of the server. Information on why or how this state of affairs has happened to get to this point is not availalbe. We look after a large number of these servers and have cross checked all optional settings within SMTP to no avail. If we add an additional port within the default SMTP default virtual server within exchange on port 26 we can connect via telnet and receive the banner from the SMTP service from inside the network and over the internet. We have tried to use port redirects on the firewall to get around this but port 26 only responds when connected to directly. If we redirect it to 25 on the public side of the firewall it does not respond.  

This is a single network card installation with all the latest patches applied. I have read that the fault may relate to RAS so I have disabled and reenabled that to no avail. I have also read that implementing a second network card and activating the firewall on the server might resolve it but I would now want to understand why this is happening.

The server was running Sophos but we have removed that already to no avail. Policy manager appears to be the default configuration. much obliged for your help.
Question by:Brontide
LVL 16

Expert Comment

ID: 18053336
Can you check within the default connector and see if it is accepting only or denying all but the address of the server and localhost?


Author Comment

ID: 18055823
Hi Adam

It's set to all except the list elow which is blank

Accepted Solution

envintl earned 500 total points
ID: 18059951

what type of isp are they using?  is it an isp like charter or comcast that normally blocks port 25?  I know here at my home that is the case unless I pay for a business account.  


Author Comment

ID: 18062986
Hi Sean,

Thanks for your input . They are using Demon, we called them first thinking they were causing the problem and we changed the firewall as well just in case there was a fault there, then we discoverd we can't connect to port 25 even from the LAN. Outlook 2003 connects to the server successfully and they can send email using the exchange on the server.
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Author Comment

ID: 18071209
Correction we can connect to the server on port 25 from the LAN. However even with a VPN connection opened to the server it is not possible to connect to the internal IP address on port 25
LVL 74

Expert Comment

by:Jeffrey Kane - TechSoEasy
ID: 18073838

If you'd kindly post a compelete IPCONFIG /ALL from the server that would certainly help in determining what's going on.


Author Comment

ID: 18075449
Got there!!

Used redirect on the firewall mapping port 26 public to port 25 private we got the banners. This meant that it had to be the ISP. Back on to Demon and only because of becoming completly belligerent, spending over an hour and a half of persistance, contacting their support plus team, repeateatly asking for supervisors did someone actually check what was wrong.

Well done Sean.

They claim to have blocked port 25 because there was SPAM coming from the customers site, they blocked 25 inbound not outbound; muppets!


Expert Comment

ID: 18087256
good to hear that you got it resolved.  I am suprised that you could not connect via vpn (if I read your responses correctly)  but as long as you have it going, we will run with it....



Author Comment

ID: 18087337

Just waiting on Demon to finally remove the block which they still claim is outbound............... I had one of their supervisor (who I will name if that's permitted? at least he took my call unlike the others!) remote desktop onto the server and open outbound 25 just to prove his colleagues are clueless.

The same supervisor gave me another supervisors name to call tomorrow morning who's part of the abuse team 12, still waiting. Thankfully the dns record is under the charge of an even worst company who have failed 3 times to make the correct mx record adjustment and therefore mail is still receivable............

Where has customer service gone??????



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