Server disconnects when getting bSMTP-mail

Hi experts,

I have the following situation:
Exchange2000 which will fetch the mail from a bSMTP-server somewhere else.
It was all working fine, till a month ago, then a lot of emails were not arriving at our server.
I called with the ISP and other people, and I narrowed the problem to the following:

When I telnet the server from the local network at port 25, I get the expected reaction like 'ESMTP Exchange Microsoft.......'
But when I telnet the server on port 25 from the internet, then the server disconnects the telnet session in half a second.

When I do above for port 110 (POP3) there is no problem. I removed all the rules in the firewall.
Sometimes an email will arrive...

Please help me, cause all my colleagues are complaining about this problem


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What90Connect With a Mentor Commented:
Hi p_sie,

Is the exchange server taking to a smart host to retreive all the messages for your site, if it is check the frequency of pulling down the email in Exchange, try to make it a shorter time frame.

If it isn't that

From the sounds of things it could beeither your router or firewall is mis-configured.
Check that no new rules or configurations have been made to your Router. If the ISP maintains the router,ask them to check the config.

Recreate the rules on the firewall for incoming/outgoing rules SMTP traffic to your exchange server and do a couple of send/retreives to some web based email accounts for testing purposes.
p_sieAuthor Commented:
What90, thank you for your comment.

The frequency of pulling down the email is every 15 minutes and is set at the advanced tab of the SMTP-connector. Furthermore it is also on that tab, that it should
request ETRN/Turn from a different server including the correct server (Checked that allready).

I did a hardware reset of my router and deleted all the rules.
Sending mail is no problem, recieving is.
Have you tried putting back the rules on the router that were working to allow incoming smtp mail to your exchange box?

Have you enabled reverse looksup on the exchange server?

When you send an email to your Exchange account from a web based site (like hotmail) do you get any error messages back?
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p_sieAuthor Commented:
>Have you tried putting back the rules on the router that were working to allow incoming smtp mail to your exchange box?

Yes I have, no result

>Have you enabled reverse looksup on the exchange server?

Don't know what that is!

>When you send an email to your Exchange account from a web based site (like hotmail) do you get any error messages back?

Sometimes it arrives, but most of the time, you get an email back after two weeks saying that the server dropped connection.
That returned mail comes from ISP...
VahikConnect With a Mentor Commented:
p_sieAuthor Commented:

that is not my problem  , cause we have an Alcatel Speedtouch 510 modem/router
P sie the easy way to make sure ur router is the problem just put ur exchange directly on the internet If possible and telnet
to it.As long as u cant telnet to ur port 25 from outside u will not be able to recieve could be the router or router
configuration.Sorry i was not much help to u.
p_sieAuthor Commented:
I cannot put my exchange server directly on the internet, cause the Alcaltel Speedtouch is an ADSL modem and router in one, tried it with an USB ADSL modem, but
my server does not have an USB port.

But isn't it strange that sometimes email does arrive?

If your pulling the email from another server, the ISP, then are you saying that new emails go to the ISP email server first, then your server pulls them down from the ISP server?

If that's the case, use a outlook client to connect to the ISP's server and see if it can retrieve emails for your server.

If it can't or it's missing emails, then contact the ISP and pass on the what you done. They need to check their end to see if you are connecting correctly and that you have the correct info for accessing the server.
p_sieAuthor Commented:
It is bSMTP, that means that the ISP collects all the mail for our domains, then when our server sends a request to the ISP , it will send all the mail to our server.

I allready contacted the ISP, that was one of the first things I did, but they told me everything was working fine, and they came up with the fact that
our server drops the connection when you telnet to port 25.

But how can the behaviour of the server for responding to port 25 change from one day to theother?

Thanks for thinking with me...
p_sieAuthor Commented:
Tested it with another modem and that did not change anything, so it has to be the server itself!
Any ideas?
I wonder if something else is trying to use port 25...have you scanned for viruses on the server and checked you firewall logs to see if you are getting any strange activity(trying to connect to odd sites etc) from your server?

Is there any other applications running on the server?
p_sieAuthor Commented:
Yes the server is used for:
- ftp
- http
- Sql-server is running
- Exchange

I don't have a firewall log, cause it is a hardware firewall
Have you added any of these services recently or made any changes to them?
p_sieAuthor Commented:
No I didn't.

The only thing  I can thinking off without get hands on with the machine, apart for the possible virus/spyware infection, is to run netstat and see what program is running on port 25. To see if it's Exchange or something else. is one way to do it or use a tool like:

I'd then try a email update and see it the app changes from exchange.
p_sieAuthor Commented:
I found the problem, it was because our ISP has a new server and it's IP-address had to be added to the list of servers allowed to relay mail to our server...

Thank you all for your help, for all the effort you made, I will split the points...
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