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Changed Telco providers, exchange not receiving over new IP address

Posted on 2013-01-31
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Last Modified: 2013-02-05
Our company has switched internet providers, and we are finally able to disconnect the old providers equipment (waited until the end of contract).  The only part of our infrastructure currently using the old services is Exchange.  I've asked our host to update our MX records, and they've added a second MX record to points to the external IP of the new internet provider.  I think I've got that covered.  

When I change the default gateway of the exchange server to the new internet service, mail is sent externally without issue.  Incoming mail is not received though.  When I run a smtp test on MXtoolbox to the new IP, I get Failed to Connect with the following transcript:

1/31/2013 9:53:51 AM Connection attempt #1 - Timeout occurred due to inactivity. [16.22 sec]

A port scan on MXToolbox shows Thread aborted.  

The fine folks at Sonicwall have told me that the connection is configured properly for Exchange.  We have an access rule setup as:

WAN > LAN Source ANY Destination X1 IP Service ExchanceServer Services Allow

The ExchangeServer Services group includes:

HTTPS, IMAP4, POP3 an SMTP.  

Any help/suggetions would be greatly appreciated.  I'm hoping to get this all moved over on Saturday to minimize the impact on workers in the building.  

Thanks all.
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Question by:Sma11T0wnITGuy
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EastThames earned 500 total points
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I assume the Sonicwall is doing NAT for your internet access? Then you need to have a NAT inbound rule which maps your external IP to an internal IP (the hub transport) on TCP port 25 (SMTP).
To test it connect a laptop to the internet outside your corporate network and run the command: telnet yourexternalIP 25
If successful you should see the exchange server banner returned. If not check your network / firewall set up.
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by:Sma11T0wnITGuy
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Good catch.  I found there NAT rule and it was pointing to 0.0.0.0 instead of the internal IP of the exchange server.  So that worked, but when I switched it over, OWA did not work externally.  I think that's the last piece of the puzzle.
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by:EastThames
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OWA is on https, TCP port 443. Make sure the there is a NAT rule for that port as well, this time pointing to the client access server.
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by:Sma11T0wnITGuy
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I'm starting to think its actually a DNS issue.  The NAT rule is already in place for all exchange services.  The DNS entry for OWA is pointing to the old IP.
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by:Sma11T0wnITGuy
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Thank you for your assistance.  I'll be opening another question for the DNS issues.
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