Cross-Forest Migration Exchange 2010 (Source) and Exchange 2013 (Target) Free/Busy with Shared namespace RRS feed

  • Question

  • Hello All,

    Many thanks in advance for the assist with my issue!

    This project is through a company acquisition, we are in the midst of a 2008 R2 AD inter-forest migration using ADMT and also an Exchange cross-forest Exchange 2010 (Source) to Exchange 2013 (Target).

  (Exchange 2010 SP1 RU8)

  (Exchange 2013)


    • The client had started the email re-branding process via SMTP alias for the
      • Reply address is now
    • Two-way domain trust between and
    • I used FIM to create the cross-forest mail contact, is not visible in in the GalSync OU with the primary SMTP address of


    My issue is with Free/Busy and I assume the issue is to do with SMTP the easy fix would be to set the original SMTP address back to the AD object but this is not viable do to the optics of having any trace of the old company name a very sensitive subject.



    I have tried the following configuration with differing results



    How can one start to troubleshoot Cross-Forest Free/Busy with Shared Namespace?

    Friday, November 16, 2018 8:04 PM

All replies

  • Your title says Exchange 2007 source but you say Exchange 2010 in your description.

    You can try creating a mail contact in one domain having a PrimarySMTPAddress of and a TargetAddress of  I'm not sure that will work but I seem to recall something about that working.

    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Celebrating 20 years of providing Exchange peer support!

    Friday, November 16, 2018 8:48 PM
  • Hi,

    - configure virtual directorys correct on both CAS Server ( and

    - create two way trust

    - check certificate validation from source to destination and destination to source

    - enable mrs proxy on source

    - use migration smtp domain ""

    - client proxy exceptions for "*"

    2)set on source "" dns a record to Exchange CAS on target

    and autodisocver srv records for this

    3)set on target "" dns a record to Exchange CAS on source

    and autodisocver srv record for this

    4)Add-AvailabilityAddressSpace -ForestName "" -AccessMethod PerUserFB -UseServiceAccount $true on both CAS

    5)Get-MailboxServer | Add-ADPermission -Accessrights Extendedright -Extendedrights "ms-Exch-EPI-Token-Serialization" -User "<Remote Forest Domain>\Exchange servers" on both CAS

    6)copy user with admt from source > target

    7)create mail enabled user on target

    8)prepare move request

    9) set on target exchange mail enabled user "target adress to "" and "send as to"

    10) move request

    11) set on source exchange mail enabled user "target adress to "" and "send as to"

    Client ask for free/busy to user in target

    Exchange lookup User with target adress ""

    Exchange use availbility address space for ""

    Exchange use from source DNS

    Exchange gets autodiscover.xml from target Exchange

    Exchange read

    Exchange connect to target Exchange to /EWS

    Exchange read Free/Busy and send to user

    If you want to use Calendar delegation and permissions in coexistenc phase you have to use linked mailboxes for move request

    • Edited by alpina27 Saturday, November 17, 2018 12:15 AM
    Saturday, November 17, 2018 12:13 AM