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Thursday, May 23, 2024

How to Configure Cross forest connectors (Mail flow) Exchange 2010 to Exchange 2010


Source Domain – CareExchange.in

Target Domain – TargetExchange.in


Lets say CareExchange.in is migrating mailboxes across forest to TargetExchange.in

For Exchange TestUser@CareExchange.in  is migrated from CareExchange.in to TargetExchange.in

But still the administrator looks for a solution that TestUser has to receive email of “CareExchange.in” , Until the migration gets over completely. (As Mx Record will be changed only in the end of the migration)

Its kind of setting up cross forest coexistence mail flow between Two Exchange 2010 Forests.


Configuring Accepted Domains  –


First Make Sure – The Domain is Set to Internal Relay (In Source Domain – CareExchange.in)

Organization Configuration – Hub Transport – Accepted Domains – Right Click Properties


And Login to Target Domain – TargetExchange.in

Organization Configuration – Hub Transport – Accepted Domains – Right Click New Accepted Domain




Configuring Send Connector on the Source Domain (CareExchange.in) –

Note : (CareExchange.in) Email Hits the Source Server . Searches for the user ,

When User Exists , Email is delivered

When user does not exist , Send the email to the target domain .

When User does not exist on source and destination domain , there is a possibility where NO NDR Gets generated

So try to Have this solution for a short period of time.


Login to Exchange 2010 Server – (Domain – CareExchange.in)

Organization Configuration – Hub Transport – Connectors – New Send Connector

Name  – Cross Forest Connector

Intented Use – Custom


Address – CareExchange.in (SourceDomain)

Cost – 1

(If you already have a connector with Cost 1 – No problem , Please continue)



Choose – Route Email Through the following smart hosts

Enter the  Destination Exchange Server IP address.

Make Sure IP is pinging and reachable



Choose Authentication is None

If you wish to use TLS , Follow the below link




Now Send Connector is Configured on the source Domain



Configuring Receive Connector on the Target Domain (TargetExchange.in) –

Login to Exchange 2010 Server – (Domain – TargetExchange.in)

Server Configuration – Hub Transport – Default Connector – Right Click Properties



Click on ADD  – Receive Mail from Remote Servers that have these IP Addresses

Enter the Source Domain Exchange Server (CareExchange.in) IP Address

If you have Mutiple HUB Servers configured on the Send connector

Make sure you add all the HUB Transport Servers IP address


Add the IP – Apply – Ok




Hope I made it clear


Satheshwaran Manoharan
Satheshwaran Manoharanhttps://www.azure365pro.com
Award-winning Technology Leader with a wealth of experience running large teams and diversified industry exposure in cloud computing. From shipping lines to rolling stocks.In-depth expertise in driving cloud adoption strategies and modernizing systems to cloud native. Specialized in Microsoft Cloud, DevOps, and Microsoft 365 Stack and conducted numerous successful projects worldwide. Also, Acting as a Technical Advisor for various start-ups.

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  1. Dear Satheshwaran,

    I want mailflow architecture between external domain (like gmail) to our organization. how they find our domain to deliver mail in ISP. could you please share any valuable document to refer?


  2. Dear Satheshwaran,

    I’ve worked thru this a few times and each time I configure it I end up with a local loop was detected. My configuration is slightly different as I built a 2010 CAS/HUB server in my Exchange 2003 environment, in hopes to use this functionality. If you have any additional information/direction it will be greatly appreciated.

  3. Hi I have two different domains in different forests.
    1. sunit.com (username:-pavitar@sunit.com)
    2. adi.com (username:-pooja@adi.com )
    I created the send connector on adi.com and receive connector on sunit.com.but still.there is no any mail flow between both domain users.

  4. Hi Satheshwaran, You have shared good step by step information. i really appreciate your work. I was founding problem with setting the connection between both domains. Actually in scenario i was looking for any automated tool for the same and found http://www.exchangemigrationtool.com hopefully it will help in to do cross forest migration automatically.

    Thanks for your informative information.


  5. Hi,

    I’m setting up a test exchange servers within out test lab for a internal project to test email flow between two exchange forests. for example. abc.com (EX2010)and xyz.edu (EX2013) both are in same network.

    I wanted to send emails from user1@abc.com user1@xyz.edu I have the send connector and received connecters created and set. But, When I send email from my EX2010 to EX2013 users. Emails are queued with NDR: Final-Recipient: rfc822;pranav@crmex2013.int
    Action: failed
    Status: 5.7.1
    Diagnostic-Code: smtp;530 5.7.1 Client was not authenticated
    Remote-MTA: dns;xyz.edu

    Any guidance will much appreciated.


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