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Exchange Server 2008 cannot receive emails from outside

I have Exchange Server 2008 that has been working fine for 2 years. All of a sudden, we are unable to receive emails from outside. Internally we can receive and send email. We can also send email to the outside world.
I have spoken to MIS Group, DNS Group and Tech Support at AT&T. Name services, MX Record and DNS are all good. I can ping the Exchange Server and also remote into the server. All services for Exchange are running; I can also telnet the server on port 25 with an answer 220-Ready to accept mail; but I cannot telnet from outside the network.
Please help....
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sti007
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sti007
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6 Solutions
 
Manpreet SIngh KhatraSolutions Architect, Project LeadCommented:
Is the transport service running and free space on drive on the HUB ?

Is there a firewall in between the Exchange and Internet ?
What does your MX point to ? If a firewall hope the port 25 isnt blocked ? Check the firewall isnt down or issues on it :(

- Rancy
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John HurstBusiness Consultant (Owner)Commented:
Presumably the Exchange Server is behind a firewall. Is it practical to reset or temporarily replace the firewall. This seems a likely test as Exchange is otherwise running and you have checked out the setup.

Go to www.intodns.com and put in your mail server IP address. That may help show anomolies we have not thought about.

.... Thinkpads_User
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sti007Author Commented:
I went to EMC--Server Config---Hub Transport---Default Receive Connector; and right click on properties--Permission tab; Anonymous was already checked.

Also, the server has 60% of its hard drive space left.

No other Firewall between the server and the AT&T Router.

I also went to www.mxtoolbox.com and did an MX lookup of my mail server; it returned with the correct IP address, domain name, and TTL=3hrs. But when I ran smtp diag, it timed out with the following error

Timeout occurred due to inactivity.
Status       Result
      Failed To Connect
Session Transcript:
8/29/2012 3:11:03 PM Connection attempt #1 - Timeout occurred due to inactivity. [16.22 sec]
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Manpreet SIngh KhatraSolutions Architect, Project LeadCommented:
try checking Inbound and Outbound email flow at

www.exrca.com

- Rancy
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sti007Author Commented:
I went to www.exrca.com and ran the tests. Everything checked out OK except for the following error:

      Testing TCP port 25 on host mail.domain.com to ensure it's listening and open.
       The specified port is either blocked, not listening, or not producing the expected response.

Everything seems to be pointing to the fact that port 25 is being blocked by certain device. I only have an AT&T managed Router/Firewall between the Exchange Server and the outside world. And AT&T logged in and checked their equipment and told me they are not blocking port 25.

Thanks for all the help so far; I feel like we are getting closer but still cannot receive emails from outside my network.
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John HurstBusiness Consultant (Owner)Commented:
Also try www.intodns.com as well as what you have done to see if this sheds a different light.

Have you asked AT&T to replace the modem with a different model?

.... Thinkapds_User
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Manpreet SIngh KhatraSolutions Architect, Project LeadCommented:
Testing TCP port 25 on host mail.domain.com to ensure it's listening and open.
The specified port is either blocked, not listening, or not producing the expected response.

What is the MX pointing to and hope port 25 is open to receive emails :)

Can you do a telnet to the MX IP and drop an email ??

- Rancy
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sti007Author Commented:
Big thanks to Rancy and Thinkpad_user. My Exchange server was fixed today. The websites and suggestions helped to trace the problem properly and  demand that AT&T Tech Support send me the configuration of their Managed Router housed onsite. Upon receiving it , I found an error. They had port 25 pointing to a private address of Barracuda Firewall which had earlier been removed from the network. Once AT&T pointed port 25 to the correct private address of the Exchange Server, I started to get incoming mails from outside the network. What a relief!!!!

GUYS, THANKS A MILLION!!!!!!
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John HurstBusiness Consultant (Owner)Commented:
Thank you for the update and I was pleased to help you with this. ... Thinkpads_User
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sti007Author Commented:
Using www.intodns.com  www.mxtoolbox.com and  www.exrca.com confirmed that a device is blocking port 25. Asking AT&T to change  the configuration of their Managed Router to reflect the correct private IP address of the Exchange server and removing the old IP address of Barracuda Firewall which had been previously been removed from the network HELPED RESOLVE PROBLEM.
It was surprising that the config worked Ok for 13 months until someone rebooted all the Switches, Routers and Servers.
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