Re: Unable to telnet into port 25
- From: Mike <fyta4_@xxxxxxxxxxxx>
- Date: Tue, 30 Sep 2008 20:04:34 -0500
Do yourself a favor before you pull out your hair and give yourself contusions from banging your head into the wall...
Call your ISP back and ask them to send you a message from their network. If that message arrives then all is good on your end of the pipe. If they cannot connect to your exchange server from their office (presumably on the same network as your router) then the problem is either with the ISP end or your end of that line between those two points. Testing this from any other place than from someplace on the same network that you are on but outside of your LAN is adding at least a third (if not more) unknown into the fray which will make it more difficult to find the problem.
TO test your end of things, wait until after hours and plug a computer in where the router is (assign it the same IP config as the router), you will either need a X-over cable to replace the cable between the router and whatever is plugged into it, or get a cheap hub/switch to do the job before your computer will look like the gateway router to your network. Now attempt to telnet in to your SMTP server on port 25. If that works then the ISP MIGHT be lying to you, if it does not work, the problem is on your side of the equation since you have just eliminated the router and everything beyond it.
Note: Test the computer first from within your network and make sure that it can connect via port 25 in a telnet session. If it can't you have other issues and are barking up the wrong tree on the wrong side of town for that matter.
If the test where you replace the router with your computer succeeds, it is possible that the problem could be with whatever network the Outlook Express client is connected to, which you will have zero control over that, especially if they are mobile users. So in this case I would suggest doing what I did for one company.
That company used a smarthost (their ISP) for both in and out bound e-mail with the internet at large. Because of that I was able to configure Exchange to ONLY accept port 25 traffic from that particular ISP host(s). That configuration will eliminate some spam and any efforts at using your server as an open relay host from outside the ISP's network. Then for the users outside of the company's network I configured them to send their e-mail on port 2525 and set up exchange to accept traffic (after authentication) on that port as well.
Since you know who the senders are going to be outside of inbound internet mail coming from a smarthost there is no reason you can't use a custom port number for their traffic. As well, since the company in question used an anti-spam system that sometimes got bogged down and delayed inbound mail for a short while I was able to configure this solution so that it completely bypassed the Anti-spam system and went directly to the Exchange Server, no need to check for spammers when the only ones connecting to that port will presumably be internal employees unless some fool spammer with a port scanner goes testing for a SMTP server on non-standard ports which would typically be a waste of time, easier to find an open relay or hijack some computers and turn them into spam bots.
MDP
Admin Matt wrote:
On Aug 29, 1:55 pm, "Leif Pedersen [ MVP]".
<leif.pedersenNOS...@xxxxxxxxxx> wrote:
Hi,
The router must be configured to forward port 25 to the exchange server - is
that configuration made?
Leif
Very good question Leif. The ISP, who are the only ones with access to
our router configuration, said it wasn't blocking port 25 but that
doesn't mean it knows to forward the port traffic to the correct
server. I'll look into this with them.
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