hybrid in multi domain with 1 Exchange server 2016

Question

We have 1 HQ domain. I named it hq.local.
We have 2 subdomains, named sub1.hq.local and sub2.hq.local.

In hq.local: no users, no Exchange server, no mail objects.
In sub1.hq.local: users, 1 Exchange server 2016, many mail objects (contacts, mailboxes, ....)
In sub2.hq.local: users, no Exchange server, mail objects (mailboxes on the Exchange server in sub1.hq.local, ...)

Goal: We want to setup a hybrid connection with 365 with the users of sub2.hq.local. And that is easy (AD connect, ....) but because of the other domain I don't know how it is configured for the mailboxes. Do I have to run HCW in the sub2.hq.local domain or in the domain with the Exchange server?
If I use AD connect in the sub2.hq.local will it be possible to communicate with the Exchange server in sub1.hq.local?

Does anyone have some useful tips for this situation?

And after that setup, is it possible to connect the users in sub1.hq.local also with another onmicrosoft account and with their mailboxes from that same Exchange server I used already in the setup of sub2.hq.local?

Thank in advance for your knowledge!!

Kind regards
Kurt

Answer 1

@Kurt Stichelmans

One forest with multiple domains could run AAD Connect successfully: Single forest, single Azure AD tenant

For Exchange HCW, you need to choose an Exchange server as end point, so even if you are running HCW at "sub2.hq.local", you still need to choose "sub1.hq.local" as the endpoint, due to Exchange hosted on it. (It is same to run HCW on sub1.hq.local)

If you want to use "sub2.hq.local" as the endpoint, you need to install an Exchange on it coexist with another Exchange server. Then choose this new Exchange as endpoint.

Another thing you need to pay attention to: ".local" domain isn't supported hybrid, you need to change it to ".com" before running HCW.

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