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Hello Everyone, first post.

My organization currently has an on-premise 2010 Exchange server that is synchronizing the mailboxes (about 260 of them) with Exchange Online (Office 365). I plan on switching over the MX records to Office 365 next week and then running DirSync so users can use their current passwords to log into O365 (can’t run DirSync until then or else synchronization stops working). Hopefully everything runs without a flaw, as most of our employees connect through OWA anyways and not the client (could cause troubles…different problem).

A week after this is all to occur, we are receiving a couple new servers virtualized with Hyper-V, and this will completely replace the current set up we have here. My question is: When I uninstall DirSync on the old server, migrate the AD to the new server, and re-install AD and point it to our O365 environment, will it resync on-premise accounts properly with 0365 (like nothing happened), or will it over-write the 0365 accounts with the on-premise accounts (and potentially deleting user’s mailboxes as well)? Or will it not even sync.

I’m hoping for the first option. Any help is appreciated

2 Spice ups
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As long as you’re keeping the same AD domain, you’ll be fine.

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Great, thanks!

One more question if you don’t mind: Many of our users are outside of the on-premise environment and use Outlook Anywhere with their Outlook client to connect to the Exchange. Their outlook clients use a proxy address “webmail.domainname.com” to connect to our local server. When we switch over our emails and point to the new MX records, my thoughts are that these users won’t be receiving any new email until their Outlook clients are pointed to Office 365, correct? Is there anyway to create a seamless transition that doesn’t involve me touching everyone’s workstation?

Thanks.

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Correct, the switchover for Outlook will need to be done in order for your clients to get new mail. You can set a CNAME for mail.domain.com to portal.microsoftonline.com. That’ll at least get their OWA access in the interim.