I have a shop which formerly had an Exchange 2010 server in-house but was moved to Office 365 some time ago. The Exchange server was decommissioned and staff use Outlook 2010 configured for the o365 servers. They're now interested in setting up dirsync, and more specifically, password sync to manage all the o365 accounts via in-house AD so users only need one password to keep track of.
First, note that their in-house domain is not internet routable (contoso.local) so I've added a UPM (contoso.com) which matches their email domain. The in-house domain and the UPM\email domain, however, do not match each other, so it's more like contosox.com vs contoso.local.
The OnRamp for o365 where I test the environment before enabling synchronization only offers 3 scenarios: fresh start, mailbox migration, and hybrid. This isn't really any of those.
I have several questions that I'm not finding clear answers for.
How does dirsync identify and match up the existing mailboxes in o365 with the corresponding user in AD? Or can it only create new mailboxes based off the AD objects?
As an extension of the first question (if we're not full-stop from it), there are several service accounts which have o365 mailboxes but no AD object and vice versa. Should I make AD objects\can I skip mailbox creations?
The first half of the user email address matches the AD login, but as noted, the in-house domain does not match their email domain (and I used the email domain as the alternate UPM). Do I have to change each user's config in AD to the alternate UPM? Is this how I can associate AD users with the existing mailboxes? This has the downside of making their in-house login names become their full email address when the goal here is to simplify things.
Basically the documentation is incredibly iffy but there are warnings all over about how dirsync should be considered permanent while fixing things post-sync is extremely complicated so clean up AD first. Not a very nice combo. Can someone with more experience with this product comment? I can provide whatever additional info you need. Thanks!