Exchange 2003 - 2010 - There is currently no route to the distribution group expansion server

I'm on the last final steps from migrating from Exchange 2003 to Exchange 2010. All mailboxes are on 2010, I removed the smtp routing group connector from the servers and shutdown Exchange 2003.
Email is flowing fine except for certain internal emails - example, when I do a test smtp from an application or email coming from sql alerts to an IT distribution group, etc. I went into the 2010 Queue viewer and saw alot of emails in the "unreachable domain".

When I click on the "unreachable domain" queue I receive the error (screenshot)



When i click on one of the stuck emails I receive the information\error:
Identity: abc-MAIL2010\Unreachable\10419
Subject: Test message
Internet Message ID: <53ddf269-8611-463b-bf75-94d5fcffd2ad@abc-MAIL2010.abc.local>
From Address: smtptest@barracudanetworks.com
Status: Ready
Size (KB): 1
Message Source Name: SMTP:Relay Connector
Source IP: 10.1.10.30
SCL: 0
Date Received: 12/20/2011 10:44:58 AM
Expiration Time: 12/22/2011 10:44:58 AM
Last Error: There is currently no route to the distribution group expansion server
Queue ID: abc-MAIL2010\Unreachable
Recipients:  opsys@abcsites.com


I have already created a relay connector on the 2010 server with all subnets included.

I noticed on one of the Distribution List properties>Advanced Tab> that the "Set expansion server" was the 2003 server, I just changed it to the 2010 server. Why is this? Shoudlnt they all be on the 2010 server? How can I fix all this? Help!

How can I resolve this? error
LVL 7
tolinromeAsked:
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Gary ColtharpSr. Systems EngineerCommented:
Did you also modify your relay connector from the Exchange Shell to allow anonymous?
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tolinromeAuthor Commented:
I didnt use the Exchange shell but EMC and yes allow anonymous is seected.
The routing group connector between the two servers has been removed. I thought this was safe since there were no user mailboxes on the 2003 server and the PF's have been moved to 2010 as well. So I assume there would eb no reason for mail to transfer through it anymore.
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tolinromeAuthor Commented:
I recreated the routing group connectors between 2003 and 2010 and the stuck emails flowed out of the queue. The question is how is mail still flowing through there when everything is pointing to the new 2010 Exchange server?
When 2003 was shut down email was flowing fine except for what seemed to be some messages stuck in the 2010 queue going to a DL. When I recreated the routing group those emails left the queue right away.
Whats going on?
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tolinromeAuthor Commented:
This solved the problem:

Get-DistributionGroup | where {$_.ExpansionServer -ne "$null"} | ft Name,ExpansionServer


Get-DistributionGroup | where {$_.ExpansionServer -ne "$null"} | set-distributiongroup -ExpansionServer $null
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tolinromeAuthor Commented:
This solved the problem:

Get-DistributionGroup | where {$_.ExpansionServer -ne "$null"} | ft Name,ExpansionServer


Get-DistributionGroup | where {$_.ExpansionServer -ne "$null"} | set-distributiongroup -ExpansionServer $null
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