We recently upgraded a client from Server 2012 + Exchange 2013 to Server 2016 + Exchange 2016.
Most everything has gone swimmingly; however, the suggested contacts (the contacts that show up as autocomplete options in Outlook) were not migrated. Prior to Exchange 2013, these were an NK2 file on the user's machine. In Exchange 2013, these became a folder in Exchange and the NK2 file was deprecated.
So, when we exported the mailboxes from the client machine for import into the new 2k16 exchange server, they should have come with.
But they didn't.
Where are they? How do I get these migrated over?
Did you check out https://support.microsoft.com/en-us/help/2199226 ?