Exchange 2013 & 2010 hybrid environment

Hello Experts!

I'm in the middle of moving our exchange organization from 2010 to 2013. I have 2 dag 2010 servers with all roles on each. No CAS array. I also setup dag with 2 2013 all roles. I'm using round robin to balance incoming traffic to new 2013 servers. I know NLB would be better but the nature of our multi-office environment will not allow NLB to function properly.

So far so good.

I created few test mailboxes on old servers and successfully migrated them to new servers. Outlook Anywhere worked fine on the inside and on the outside. Outlook picked up new servers without the problem after restart. Mobile devices have to be reconfigured for new servers and Im okay with that.

I'm concerned about mail flow. It flows fine between mailboxes on new servers. It also flows fine from mailboxes on old servers to mailboxes on the new servers. It gets delayed and eventually fails latter when sent from mailboxes on the new servers to mailboxes on the old servers.

I checked DNS and everything seems to be in order. Round Robin is also setup on the inside and servers can reach each other with public DNS.

Not sure if this is relevant to the problem I have but I ran "Remote connectivity Analyzer" and it fails "  RPC over HTTP connectivity failed. " I also ran Test-OutlookConnectivity -ProbeIdentity "OutlookRpcCTPProbe" and it completes successfully

Any advise will be highly appreciated.

Thank you
Roman PomahAsked:
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Can you provide the NDR message you see?
Roman PomahAuthor Commented:
Fist Last (
The recipient's email system isn't accepting messages now. Please try resending this message later or contact the recipient directly.

Diagnostic information for administrators:
Generating server:
Remote Server returned '550 4.3.2 QUEUE.Admin; message deleted by administrative action'
Original message headers:
Received: from ( by
 ( with Microsoft SMTP Server (TLS) id 15.0.847.32; Fri, 14 Nov
 2014 13:13:27 -0500
Received: from ([::1]) by
 ([fe80::c52b:ead1:a0a0:35e5%22]) with mapi id 15.00.0847.030; Fri, 14 Nov
 2014 13:13:27 -0500
Content-Type: application/ms-tnef; name="winmail.dat"
Content-Transfer-Encoding: binary
From: test user1 <>
To: Real User <>
Subject: 113
Thread-Topic: 113
Thread-Index: AQHQADavkn6wux/zbkqUiX72ou3kkw==
Date: Fri, 14 Nov 2014 13:13:26 -0500
Message-ID: <>
Accept-Language: en-US
Content-Language: en-US
X-MS-TNEF-Correlator: <>
MIME-Version: 1.0
Gareth GudgerSolution ArchitectCommented:
Hey Roman,

When you send a message can you check the queue viewer in Exchange 2013 and see what the Retry error is?

To take a stab at a guess, normally mail flow issues during coexistence is that the 2013 server is not permitted to relay messages to the 2010 server. More often that not it is a permissions issue on the 2010 Receive Connectors.

How many receive connectors do you have on 2010? Is it just the standard Client and Default connectors? Have these been modified in any way? Also, have you created any additional receive connectors on the 2010 side (for example for application relay).

What I often see is that an application relay was configured on the old server (normally anonymous relay) and that the IP of the new Exchange 2013 server is somehow listed either directly or through a network range on that anonymous relay.

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Roman PomahAuthor Commented:
Thank you. I actually had open relay connector on old exchange accepting traffic from where two new exchange servers are located. Once I scoped out IP addresses of new exchange servers from this connector, issue disappeared.

Now I identified different issue not sure is it's related to the previous one and if it existed before. My system messages generated on old exchange are delayed to users on old exchange. System messages such as reply from conference room or notification to the user that mailbox is almost full. Delay error is 400 4.4.7

I have one send connector with all 4 exchange servers in it. Should I separate them one send connector for old exchange servers and one for new servers? If so, how would I go about priority for each send connector?

Thank you
Gareth GudgerSolution ArchitectCommented:
Glad its resolved! Let's go ahead and close this question and open a new one. That way you can get your second question to the top of the list where more experts will see it. I will look for it as well.
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