I performed a migration from Exchange 2010 on SBS 2011 to Office 365. I'm preparing to turn off the old server and use a new DC, but for now the old server with AD and Exchange is still operational.
Everything has gone smoothly so far, and users have Office 365 directing mail to their computers. Great! However, some users are getting prompted for Exchange credentials. It turns out I need to convert their mailboxes in Exchange 2010 to MEUs to keep this from happening.
I followed all of the instructions here: https://community.office365.com/en-us/w/exchange/845.convert-exchange-2007-mailboxes-to-mail-enabled-users-after-a-staged-exchange-migration
Everything seemed on track, but then I get the following error for every mailbox:
An Active Directory error 0x51 occurred when trying to check the suitability of
. Error: 'Active directory response
: The LDAP server is unavailable.'
+ CategoryInfo : NotSpecified: (:) [Set-MailUser], SuitabilityDir
+ FullyQualifiedErrorId : FF5E0243,Microsoft.Exchang
Exception calling "InvokeSet" with "2" argument(s): "The server is not operatio
eset <<<< ('msExchMailboxGUID',$Mail
+ CategoryInfo : NotSpecified: (:) , MethodInvocationException
+ FullyQualifiedErrorId : DotNetMethodException
I've double and triple checked LDAP to make sure it's enabled and working. I've made sure my account has all of the necessary permissions, and my powershell console is being run as an administrator. I've googled my brains out, but apparently this error never happened to anyone else in the history of Office 365. I even contacted Office 365 support, but they claimed this wasn't covered by them, and that I'd need to pay for server support.
I'm hoping somebody else has seen this error, knows what causes it, and how to fix it. If I can't find a solution, it looks like the only option would be to throw the old server out the window, create a new domain, and reimage the new server.