Free busy share cross forest

Dear members,

Current working on cross forest migration between Exchange 2010 and Exchange 2013 I need to share between both Exchange free busy and calendar.

Since Federation is not available (must share smtp domain during migration), I try to share free busy using availability address space.
On source.local and destination.local I run:
add-adpermission -accessrights extendedright -extendendright "ms-Exch-EPI-token-serialization" -user "destination.local- source.local\exchange servers"
Then, add-availabilityaddressspace -forestname  destination.local-source.local -accessmethod peruserFB -useseviceaccount:$true
Last, export-autodiscoverconfig -targetforestdomaincontroller dc.destination.local-dc.source.local -targetforestcredential $target -multipleexchangedeployments $true.

Now, I can access to free busy and calendar from source to destination. I can add meetings from source to destination, but from destination to source is not possible (can not access to server).

I have some kind of galsync between forest (exports all source mailbox as contacts on destination using script, but I do some test creating MEU using prepare-moverequest), checked autodiscover on source and destination and seems to be correct.

Try to increase logging but can not find anything on event viewer.

Appreciate any help.
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Miguel Angel Perez MuñozAsked:
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Scott CSenior EngineerCommented:
See this blog about Cross Forest Free/Busy .

Make sure you've covered the 9 steps listed.
Miguel Angel Perez MuñozAuthor Commented:
Dear ScottCha, I´m afraid this is not my case. I have trusts between forest and autodiscover was exported.

Miguel Angel Perez MuñozAuthor Commented:
I found where problem was, must to give permissions "ms-Exch-EPI-token-serialization" on Exchange 2010 CAS servers and Exchange 2013 Mailbox servers.

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Miguel Angel Perez MuñozAuthor Commented:
Any comments fits on my case. Finally found after 4 days of research.
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