This Migration Guide will help you to migrate mailboxes across forest

Its always people go confused when source and target forests are Exchange 2010, I have tried to explain as detailed a possible and covered one method

where “Running .\PrepareMoveRequest.ps1 first and then using ADMT to migrate the Sid History” of the users

Please share your feedback in comments , So that I can update the guide frequently

so lets go ahead

Step 1:

Have Trust in place across forests , In my Situation I created Two way Transitive Trust where I won’t get into any permission constraints

Good to know : We can limit permissions by going for different type of trusts

See –

How to Create Two way Transitive Trust – Windows Server 2008 R2

Step 2:

You need Active Directory Migration Tool to Get your User accounts migrated without any hassle, You can install it in either of the forests but , Have installed in the target forest , where I will be doing most of my work

See –

How to install ADMT 3.2 in Windows Server 2008 R2

Step 3:

If you are planning to Migrate the User account with SID – Which is recommended – where users will still have access to their old forest where they will be recognized like

access to file shares and permission groups . So I would always recommend to get your SID along with the Users

If you are planning to Migrate Users with Password that doesn’t happen by default , You have to Configure “Password Export Server” in the source domain

See –

How to Migrate Users Across forest (Cross Forest) using ADMT 3.2 with sid and Passwords

Step 4:

Enable MRS Proxy on the Source Client Access Server which is going to Facilitate the Remote move from the Source Forest,

I have described Enabling MRS proxy where version is Exchange 2010 Sp1 or later cause enabling in RTM version differs

See-

How to Enable MRS Proxy and Increase timeout In Exchange 2010

Step 5:

Ignore if you are not using a Self Signed Cert.

If you are using a Self Signed Certificate –Where Exchange servers won’t authenticate between each other

Because they won’t trust each of them

You got to Export the Cert from Source Exchange Server and import it on Target Exchange Server

Vice versa

See –

How to Export a Self signed Server Certificate and Import it on a another Server in Windows server 2008 R2

Step 6:

Check List

•  Now Trusts are in place
• ADMT is installed on the Target DC
• MRS Proxy is Enabled on the Source Forest Client Access Server
• Admin User of the Target forest  is a member of administrators group in the Source forest – Add vice Versa
• If you are using Self Signed Cert – They have been Exported from the target and imported in source (vice versa)
• If you are planning to migrate passwords as well – Password Export Service is Configured and PES service is Started in the Source Domain

Before starting, There are many methods to Move mailboxes across forest .I will go for the Recommended one .

let us call this method as “Running .\PrepareMoveRequest.ps1 first and then using ADMT to migrate the Sid History”

We will move one mailbox to get a Clear idea , Then we can go for Bulk Migration of mailboxes.

I always recommend to move few mailboxes . Test it as much as you can . they go for bulk migration

Step 7 :

Created a Test Mailbox – Mailbox1

Step 8:

First Store the Access Credentials in the Shell

Please don’t confuse yourself Here.

Am Running this on the Target Forest – $localCredentials Means the TargetForestCredentials

SourceForest – careExchange.in

TargetForest – TargetExchange.in

Please don’t forget to Type the DomainName\UserName (Note:If it fails with Error – Authentication Failed – Try Entering Domain.Com\Username ,.com or .local refers to your local domain)

$localCredentials = Get-Credential

$RemoteCredentials = Get-Credential

Means my Source Forest

Note : After Storing your Credentials – Do not Close Shell – You got to run the Future Command in the Same Power Shell Session

Step 9:

Now Preparing a Move Request

Browse your Exchange Management Shell into Scripts Folder in your Target Forest , Which will be in Exchange installation Location

.\Prepare-MoveRequest.Ps1 -Identity EmailAddress -RemoteForestDomainController FQDN of Source DC -RemoteForestCredential $RemoteCredentials -LocalForestDomainController FQDNofTargetForestDC -LocalForestCredential $LocalCredentials -TargetMailUserOU Distinguished name of OU in TargetForest –UseLocalObject -Verbose

Using –Verbose in the end of the Command

You can clearly see what are the Attributes its getting touched

Mail,Display name,Proxy address etc..

Now you can See a Disabled account which has been Created on the Specified OU

Step 10:

Now use ADMT to migrate the SID and Enable the Target Account which is “Mailbox1”  in my Scenario

See-

How to Migrate Users Across forest (Cross Forest) using ADMT 3.2 with sid and Passwords

Now you can find the SID history of the account , Where you can confirm that you did things correctly

Now your AD account will get  Enabled

Step 11:

Now your Account with SID and password as been moved, But still your Content of the mailbox hasn’t moved yet. Which is moved my a remote as below

Now moving the mailbox using a Remote move request

New-MoveRequest –Identity 'Mailbox1@careexchange.in' –Remote –Remotehostname 'sourceExchange.CareExchange.in'  -RemoteCredential $RemoteCredentials –TargetDeliverydomain 'targetexchange.in'

Now you can See a Remote move has been Completed

Now you won’t be able logon on the new forest directly as you required to change password as first logon

To avoid that situation

See-

How to Disable “User must change password at next logon” after cross forest move using ADMT 3.2

Open Adsiedit –Set pwdlastset to –1

or just login to a client machine and change the password at first logon

Great !! you able to login in Target Forest Success fully !!

Step 12:

To Move the Users in Bulk

See-

Cross forest Move Mailbox in Bulk – Exchange2010 to Exchange 2010

Step 13:

If you doesn’t want to share free/busy information as of now. Skip it

if you want to share Free/busy information between these forests. If source domain is always going to exist after migration . I would recommend to create Federation Trust which is free of service from Microsoft to share free busy information.

if you doesn’t want to go for Federation you can share free busy using below method

See –

How to Configure Cross forest Availability Service (Free/Busy,Auto discover) – Exchange 2010 to Exchange 2010

Step 14:

Please look into the below link for configuring Cross forest coexistence mail flow

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

https://www.azure365pro.com/how-to-configure-cross-forest-connectors-mail-flow-exchange-2010-to-exchange-2010/

Happy Cross forest Migration !!

Hope I made as much simpler as I can !!

Thank you !!