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Jody DavisFlag for United States of America

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Will free/busy still be available if we drop hybrid Exch server and just go only MS O365?

We're looking at dropping our hybrid Exch server from our onprem (other reasons - no need to discuss) but besides user mgmt having to go through ADSIedit (ugh) i read something about calendar free/busy sharing of user status bein involved as well.


** If we drop our Exch hybrid server since all our mailboxes are in the cloud, using Azure AD Connect still and choose to manually edit user objects - will we loose our calendar free/busy sharing status in Outlook?


           Please provide a link, if you can, so i can share with mgmt as well.  Thanks!

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Vasil Michev (MVP)
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Thank you, couple more questions:

1. Ok, so other than having to use ADSIedit or another 3rd party tool (both i know are not supported), is there anything else you can think of that will be different/warn mgmt about if we remove our hybrid Exch server?

2. I read SMTP relay can be effected.  We currently do SMTP relay for some of our customers (they use our software) that send email campaigns through us - to users (we have to use DKIM, etc to secure and ensure no spam marking of the Co., etc) - but all our mailboxes exist in the cloud. Would that kind of relay be hindered at all? All our mailboxes are in the cloud, so i would think not as mailflow doesn't go through the hybrid server.  Any idea? 
It is recommended to keep a hybrid exchange server on premise - even once all mailboxes have been migrated so you dont have to use ADSIEdit and you can still SMTP relay through that hybrid server.

As long as there are no mailboxes on it, it does not incur an exchange license cost.

if you are dead set on removing the last server (which, by the sounds of what you have said, i would not agree with) this is a good guide to follow
https://docs.microsoft.com/en-us/exchange/decommission-on-premises-exchange

That document covers multiple scenarios... and since we don't know the detail of your setup (i.e. are you sync'ing identities via AADConnect - we assume so - but with which auth method?) - it would be good to let us know which scenario you fit into from that doc.
I'd be careful with sending mass emails via Office 365, if that's a valid business need, consider leaving at least one Exchange box on-premises, or spin up another mail appliance to handle this outside of O365. Or go with one of the services that specialize in email campaigns. Otherwise you risk your users, or even entire tenant, being blocked as mass mailers.
True, Vasil. We work hard for that not to happen.

* Hayes - we use ADFS/STS autodiscover for authentication of users and Dirsync for Azure Connect to sync our onprem AD to O365.

          - We're doin this now due to Okta SSO being implemented - it doesn't like hybrid Exch servers, i'm being told....
          - do you have any further thoughts knowing this is how we connect our AD/auth?
I have a meeting about this in 30min - can anyone answer my autodiscover question above - quickly please??

     Thanks :)
everyone has to sleep sometime Jody....

Based on using ADFS, you fall into category two within that document, which states:
Solution: Since the customer is planning on keeping AD FS, they will also have to keep directory synchronization since it is a prerequisite. Because of that, they cannot fully remove the Exchange servers from the on-premises environment. However, they can decommission most of the Exchange servers, but leave a couple of servers behind for user management. Keep in mind that the servers that are left running can be run on virtual machines since the workload is almost completely shifted to Exchange Online.

I dont know enough about Okta to be able to comment on that part.
I, of course, understand i won't get immediate responses. Just tried to get a quick answer before a meeting, is all. Gave it a shot.  Then with you being in Australia (who knew. lol) it's understandable. Of course.

     * ADFS will be staying, and Dirsync will still be around as well, of course. But this is saying i HAVE to keep the Exch server around - i know others have removed theirs. Is that meaning i need to keep it around to ensure it's supported in event of issues, or if i use ADFS and Dirsync/AzureAD Connect - that i MUST keep it/required?  If it's just to stay supported, we're willing to take that chance.  Is that what they're saying, the Exch server must stay, only for MS support or it cannot be removed at all?
I don't have a solid reply for that.

MS pages rarely (that i've seen) talk in absolutes - they like to skirt around things... so when a page actually bothers to say "they cannot fully remove" - i would choose to take that at what it says.

What i can say is:
- I've never removed the last exchange server for a client that uses ADFS - so i don't have any experience here to give any advice - maybe someone else will
- In any scenario with migration to O365, removing the last exchange server makes life harder as far as SMTP relay and day-to-day management
- If you are to go down that path, any forum post or support call with MS will start with "why did you do that?, that's not recommended"
- I just don't get why anyone would be opposed to leaving a single, small, virtual exchange server around for management and SMTP relay (and supportability) purposes.


Apparently my management is goin the Okta SSO route, and supposedly Okta doesn't like a hybrid server. Why this is - i have yet to be told. Lookin forward to hearin about this. Cause, like you. This server is set and forget other than Windows patches. I see no need to rock the boat either. But - supposedly Okta is the issue.

Thanks for your responses. I'll close this out.