Yes, I’ve worked a couple places where we had inbox quotas and archived old emails to our personal network drive or (if we had quotas on our network space) hard drives.
But the emails were also archived to tape. It was just a real pita to retrieve it from there.
What matters here are the NARA rules. If they were being followed then the emails should be stored on tape.
True on that. There is also the possibility of an implementation of an Exchange archive solution; where the message CONTENT for everything 90/180 days old gets archived off Exchange except for the message stub. So depending upon the enterprise setup...there is ANOTHER location for older/archived messages.