Summary

In case of any errors appear at the fist step of OBRM Exchange backup wizard (after entering Windows credentials to to connect to the Exchange server - screenshots are provided below), it is needed to localize the problem: whether it is an Exchange server issue or OBRM issue.

Solution
It is needed to provide a test connection to the Exchange server via PowerShell (from the same machine where OBRM and Exchange is installed ):
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According to Microsoft Knowledge Base Article:
https://technet.microsoft.com/en-us/library/jj984289%28v=exchg.160%29.aspx
please, open PowerShell (not Exchange PowerShell) and type following commands:
1-
type (without quotes):
\$UserCredential = Get-Credential hit Enter (The window will appear which asks you to enter credentials - enter then in form of domainname\login and password which you use to open Exchange Management Console) the user should be "Exchange administrator" and "local administrator" at the Exchange Server 2 - type (general pattern, without quotes and newlines): "\$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri http:// </strong>/powershell?serializationLevel=Full -Authentication Kerberos -AllowRedirection"
is fully qualified domain name of the exchange server i.e. email.mytestcompany.com

3 -
If the command #2 ran successfully, type:
Import-PSSession \$Session (at this step, connection to Exchange Server is established). 4 - run Get-Mailbox The command will show all mailboxes available in the Exchange database. 5 - close the session using: Remove-PSSession \$Session
> > > > > > > > > >

If the same error appears when running the above commands, the issue is caused by the Exchange Server settings or Windows credentials used to connect to the Exchange server.
The next step is to save the error message and search for solutions in Microsoft knowledge base articles.