Exchange 2010 Hybrid question


I've just taken on a new role and was hoping for some help somethingwith a hybrid migration. The company i've joined has an Exchange environment spread across London, New York and Sydney. Each site has a single Exchange 2010 server with the mailbox, hub transport and client access roles. One mailbox database per server for each locales mailboxes. No DAG or CAS array configured. The previous IT manager has also set it up in hybrid mode to Office 365.

The hybrid seems to be working ok. Directory and password sync works and I am able to migrate mailboxes to Office365 without any fuss (the profile doesn't need reconfiguring which is great).

Here is the kicker. Management want to close the London datacenter so have tasked me with migrating the London users to Office 365 and decommissioning the London Exchange. The other offices are not our responsibility so they'll migrate their mailboxes at a later stage.

The good things are that the London Exchange is not being used for any scan to email or SMTP relaying. Also, the Office365 to Exchange mail flow is going via the NY server.

My questions:

1. I can  see when i move a mailbox to O365 that Outlook still uses the local Exchange server for its RPC/HTTPS connection. When i've moved all the mailboxes across and uninstall Exchange will I need to reconfigure everyone's Outlook profiles? I hope not as there are 200+ users. I'm guessing Outlook will either use the other Exchange servers for this or else use Office 365 autodiscover provided I change the internal and external records to point to O365
2. Are there any other gotchas i should worry about when uninstalling this one Exchange server? I don't want to inadventently break anything for the NY and Sydney guys. Luckily, the old IT manager was US based so the NY server seems to be doing most of the work.

I appreciate any help or advice you guys can pass on. :)
Exchange NoobAsked:
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Patrick BogersDatacenter platform engineer LindowsCommented:

Once you moved all mailboxes to O365 and autodiscover is pointed (plus other dns settings) to the cloud you can monitor the send/recieve connector and OWA logs which should remain at the latest point.
Once you are sure this is the case you can stop the transport services on this box and wait a few days or weeks.
If this doesnt break anything it is time to uninstall exchange and decommision the server from AD.

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Exchange NoobAuthor Commented:
Thanks Patrick, that's good to know. Didn't relish reconfiguring 200+ Outlook profiles!
Jason CrawfordTransport NinjaCommented:
If you want to prevent cloud mailboxes from using the on-prem Autodiscover SCP, just convert the on-prem mailbox to a mail enabled user
Exchange NoobAuthor Commented:
Hi Jason, isn't this only available as an option in a staged migration which is Exchange 2003 and 2007 only?
Patrick BogersDatacenter platform engineer LindowsCommented:
Answer provided
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