How to manage 365 with active directory integration

Scenario:
In a Windows 2003 environment, there is an Exchange 2003 mail server. All mailboxes have now been successfully migrated to 365. There is active directory integration provided by an on premises DirSync server.

The Exchange server is still available on the network, but Exchange is no longer actively used. 2003 Administrative Tools are installed on the Exchange server and facilitate the creation of new accounts, distribution groups, general administration with the availability of the features highlighted in screenshot 1.

Screenshot 2 was taken from a domain controller (not the Exchange server), which indicates that the Exchange tabs are not present.

With the above in mind, and anticipating that administration may need to be conducted directly form 356, we added an alias directly from the 365 portal and were presented with the message indicated in screenshot 3

We want to decommission the on-premises 2003 Exchange server from the network so we can upgrade the domain from 2003 to 2012

Question:
When we fully uninstall the on-premises Exchange server this effectively decommissions Exchange from the internal domain, what measures do we need to take to ensure we do not lose administrative functionality of mailboxes, distribution groups, contacts etc..
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swan_solutionsAsked:
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Zephyr ICTCloud ArchitectCommented:
Well, there's a few options ... Mostly comes down to preferences.

Certain admins will do everything through Powershell (via a plugin) or directly via ADSIEdit (eg create an alias).

Other admins will install the EMC on another server (once they've decomissioned the Exchange server for example) just so they can still use it to perform some tasks without having to rely on Powershell or ADSIEdit.

And then there's the other admins that would go for third-party plugins to manage their Office365/AD environment
Vasil Michev (MVP)Commented:
If you want to stay in "supported" scenario, you dont decomission Exchange :) Read this article: https://technet.microsoft.com/en-us/library/dn931280(v=exchg.150).aspx?f=255&MSPPError=-2147217396

Although it speaks mostly about Hybrid, the same applies when you only have Dirsync in place.
swan_solutionsAuthor Commented:
I've since read plenty of articles where others have the same issue. Like you say ADSIEdit (or Attribute Editor for Server 2012) allow me to manage

Do you mean an earlier version of EMC (2010 or earlier)? It would be nice to continue managing mail features as we did previously (through AD user properties). I'm not aware of EMC being available through the Exchange 2013 install files?
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swan_solutionsAuthor Commented:
Unfortunately this is not a hybrid scenario and we need to decommission Exchange 2003 so we can fully upgrade the internal domain from 2003 to 2012.
Vasil Michev (MVP)Commented:
You can decomission it, as long as you are fine with the implications. Microsoft do not support managing Exchange related objects and attributes with ADSIEdit or any other tool apart from the EMS/EMC.

Which of course doesnt mean those tools will not work :) Just make sure you understand that you might end up in situation where Microsoft is telling you "this is not supported configuration".
Zephyr ICTCloud ArchitectCommented:
Yes, EMC is 2010 only ... Sorry missed a bit of the conversation so it seems ... The only other options are Powershell and ADSIEdit or as I mentioned certain third-party tools.
swan_solutionsAuthor Commented:
In order to decommission  the exchange server, mailboxes need to be deleted. As a test, I deleted and purged the mailbox of an employee who recently left the company. I then went to the Attribute Editor to add in a new e-mail alias (proxyAddress), then let DirSyn and 365 do its thing.

After a period of time, AD sync'd with 365 but the account in question did not inherit the new alias, and the default e-mail address had changed from username@companydomain.com to username@companydomain.onmicrosoft.com, and I cannot change this back?

This appears to be triggered by the purging of the mailbox.

Any thoughts?
swan_solutionsAuthor Commented:
I've figured out that when deleting the Exchange mailbox, you need to enter the following in Attribute Editor:

For the default address, enter SMTP:name@domain.com (SMTP must be upper case)
For aliases, enter smtp:aliasname@domain.com (smtp must be lower case)

From experience, if you do not enter the SMTP or smtp prefix in Attribute Editor>proxyAddresses, it will affect the default and alias addresses on the 365 portal.

This was a gap in my knowledge, so I hope this post is beneficial to others.

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Zephyr ICTCloud ArchitectCommented:
Hi ... Sorry missed the conversation somewhat so it seems ...

That is certainly useful information that will help a lot of people, case-sensitive is not always a given on Windows systems, so people sometimes overlook it.

Thanks!
swan_solutionsAuthor Commented:
Further research relating to the Attribute Editor>proxyAddresses entries provided the final piece to the jigsaw, but spravtek pointed me in the right direction.
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