Multiple forests, single Azure AD tenant

[Off2w0rk]

Hi all,

Here is current setup

One O365 tenant with

One AD forest name domainA.com

One AD forest name DOmainB.com

There is full trust between both forest

Both Forest have their own Exchange 2013/2016 server

Azure AD Connect is installed on DomainA.com and both forest are synced to same O365 tenant

Exchange hybrid ran successfully from both forest and Azure AD connect successfully sync AD accounts from both forest.

Question is:

Can we use same migration endpoint for both forest or do we need separate migration endpoint for each forest?

Problem is:

Migrating mailbox from DomainB.com fails, so does incoming mailflow to DomainB.com. Currently mx record for domainB.com is pointing to Exchange Online. DomainB.com have successfully been added to the tenant.

Tried to find documentation regarding this setup, but so far haven't found any.

Need advice.

thanks!

:)

[#2]

You need a separate namespace as detailed here: https://technet.microsoft.com/en-us/library/jj873754(v=exchg.150).aspx

• Namespace planning
  Each forest in which you install Exchange requires its own unique externally-discoverable namespace. You'll specify a forest's unique namespace in the Hybrid Configuration wizard when you run it in each forest.

[#3]

Thanks Vasil,

regarding namespace, it should be ok to point MX record to Exchange online?

Mail(OWA) and Autodiscover should be pointed to on-premise.

During hybrid config wizard I already did specify separate namespace (mail.domaina.com and mail.domainb.com)

Still I don't understand why emails are not delivered. I have already changed both domains to internal relay in O365. Maybe I need to create separate connector for both on-premise to communicate over. Will need to test it tomorrow when I'm back at work

[#4]

Yes you need to run Hybrid Wizard it will setup the connectors for you !  

[#5]

Hi Simon,

as mentioned earlier the HCW have been run in both exchange environment, but still did not help.

Unified GAL is not working either, since they can only see contact from own environment. In Exchange online we do see them together.

According to earlier link, seems like everything should work by default, but it does not work for us: https://technet.microsoft.com/en-us/library/jj873754%28v=exchg.150%29.aspx?f=255&MSPPError=-21472173...