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New Exchange Server - Outlook Anywhere

Rupert Eghardt
Rupert Eghardt asked
Hi Guys,

I've setup a new Exchange 2016 server.
The server was installed into an existing AD with an Exchange 2010 installation.

All worked well and the new server is operational.

Our firewall and DNS still points to the old server for Outlook Anywhere and is working for the mailboxes still on the old server.

The issue:
As soon as a mailbox is migrated to the new server, the mailbox becomes inaccessible via Outlook Anywhere.

For example, trying to access the mailbox from OWA produces the following error:
A server configuration change is temporarily preventing access to your account. Please close all Web browser windows and try again in a few minutes. If the problem continues, contact your helpdesk.

Is there a way to have Outlook Anywhere working for mailboxes on both the old and new server via Outlook Anywhere (the same host name)?
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System Engineer

when you are doing Exchange 2010 to 2016 migration, you need to point Outlook Anywhere, DNS and firewall to a 2016 server.
Thing is that 2016 will then proxy/redirect traffic to 2010, but it is not possible the other way around.

That way when you migrate mailbox to 2016 it will work, and if some users are left on 2010, new server will simple redirect connections to 2010 server, and everything will be working for users on both server.

So, in short, configure autodiscover and all other services the same way as you did for 2010, then change DNS to point to 2016, and reconfigure firewall/ router to point ports 443 (and maybe 25 depending on configuration) to 2016 server.

Make sure Outlook Anywhere on Exchange 2010 is configured to support NTLM authentication.
If it is set for Basic, configure it with Basic+NTLM

To see and optionally configure it use:
[PS] C:\>Get-ExchangeServer | Where {$_.AdminDisplayVersion -like "*14.*" -and $_.IsClientAccessServer} | Get-OutlookAnywhere | fl servername,externalhostname,*auth*
[PS] C:\>Get-ExchangeServer | Where {$_.AdminDisplayVersion -like "*14.*" -and $_.IsClientAccessServer} | %{Set-OutlookAnywhere "$_\RPC (Default Web Site)" -IISAuthenticationMethods Basic,NTLM}

More about client connectivity in your situation:

Rupert EghardtProgrammer


Thank you!  I did not know that it was not possible the other way around,
Let me test this and revert back ...