Exchange 2016 Cross Forest vs Resource Forest

[ITGURU]

I have 2 sites which both have separate AD Forests and Exchange 2016 servers installed.

 

The plan is to setup a forest trust so users can access resources cross site from each site.

 

AS for exchange, i would like to have 1 global address list with users from both sites exchange servers and also be wanting shared calendars so users in both AD forests/sites can access calendars from either side.

 

However, do i keep the 2 exchange servers separate and set up galsync or would i be better off creating a third new Forest and installing exchange server into the forest and then using this as a resource forest with exchange on for users in both the 2 separate schools AD forest?

 

I notice from online in the supported scenarios it says you can either set up cross-forest or resource forest, but if go down the resource forest route, one of the user forests cannot have exchange installed.

 

If this is the case does that mean i cannot leave exchange on each site, and set up the new third forest with exchange to then migrate the mailboxes to?

 

Looking for a bit of advice before the project commences.

 

What i'm looking for is a central exchange environment, and if means a resource forest then having a DC for the 3rd forest at each site and an exchange server at each site also so 1 mailbox database for 1 site, and another mailbox database for the other.

 

Thanks.

[chaplic]

Wearing my MS hat the obvious answer is to none of the above, move all to a single O365 tenant.

 

You can do any of the options you said. I wouldn't not recommend a third forest as your are doing two migration programmes not one.

 

Do galsync now as you can have that setup in an afternoon. Assuming you are definitely not going O365 I would pick the newest exchange environment and base everything on that and migrate mailboxes from the other org. Your user forest you are moving people from will eventually have no exchange, so we are still supported.

 

Get really knowledgable about how linked mailboxes work and MsExchRecipientDisplayType and so on, none of this is well explained but it is out there.