NDRs after installing Exchange 2003 into Existing Exchange 5.5 site

Ok, I've got Exchange 2003 intslled into my existing Exchange 5.5 Site.  I have worked out various issues with the address list.  Now I've got outlook setup for a test mailbox on Exchange 2003.  When I try to send mail to users or DLs on Exchange 5.5, I get NDRs back.  

The MTA was unable to route to recipient DN:CN=username,CN=RECIPIENTS,OU=SERVER1,O=orgname§C=US;A= ;P=orgname;O=Server1;S=userlastname;G=firstname;. The message (MTS-ID): C=US;A= ;P=orgname;L=TPA01EXCHG05-060415184308Z-3, recipient: DN:CN=username,CN=RECIPIENTS,OU=SERVER1,O=orgname§C=US;A= ;P=orgname;O=Server1;S=userlastname;G=firstname;, recipient number 1. Check the routing table for a possible incorrect routing configuration. [MTA DISP:ROUTER 11 119] (12)

If anyone has any tips on things I can do to try to fix this, I'm all ears.  Everything else is working great, this is my last hurdle.

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MCPJoeAuthor Commented:
To clarify, I can receive mail through SMTP from the outside, which routes through one of my Exchange 5.5 servers.  Also, Exchange 5.5 users can email users on Exchange 2003.  However users on Exchange 2003 cannot mail Exchange 5.5 mailboxes.  
go to services and make sure MTA is started(by default it is set to disabled)...
this is for 2000....but may help u figure out this problem if it has nothing to do with MTA services...
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MCPJoeAuthor Commented:
I am running Exchange 2003 with SP2, so I doubt that link will help.  I'll check the MTA service in a few minutes.

are you selecting the E55 user from the GAL or typing the address manually.
Are the E55 and E2k3 servers in the same administrative group
MCPJoeAuthor Commented:
It does the same thing if I type it manually or use the gal.  I get NDRs.  I think the issue is with the AD attribute on user accounts in AD, regarding the homeMTA settings.  I got some errors in the exchange install logs telling me there was no homemta attribute on my AD users.  I am going to call Microsoft today to try to help fix it.  
Check the following article and try to use winroute to view the routing information

Link state issues and routing issues in Exchange 2000 Server and in Exchange Server 2003
MCPJoeAuthor Commented:
I don't think thats my issue, I can send mail to external (internet) addresses just fine through Exchange 2003 mailboxes, I just can't email Exchange 5.5 users from 2003.  Also, Exchange 5.5 users can email Exchange 2003 users without a problem, but Exchange 2003 cannot reply or send any mail to Exchange 5.5.  
first u have to figure out if NDR is generated just for the moved users or for all
users ....specially the newly created users on the 2003 server....
if new users also have this problem then u have to check this...

if this is not ur problem ...then u have a routing problem....
MCPJoeAuthor Commented:
I haven't moved any users to Exchange 2003 yet.  I was able to fix the problem by correcting the homeMTA attribute in AD.  Microsoft gave me the admodify tool and I have to modify all my users to correct the value.  I had to create a test user and mailbox on Exchange 2003 to get the syntax of the correct value, then use that in all my other users attribute.  That fixed it for me.  
MCPJoeAuthor Commented:
had to modify the homeMTA values on my AD users accounts.  That fixed my issue.
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