Voicemail capacity and employee off-boarding

When we off-board an employee I am sometimes left with a voice mailbox containing hundreds of messages.  Typically they are marked as read so I assume that the messages have been resolved.  Is there any way to force messages be deleted?  A mailbox capacity limit would accomplish this but I don’t see that as an option.

Any other thoughts on how to encourage users to delete messages after they are no longer needed? 
Can an admin see which users have a large number of messages in their mailbox short of granting themselves access to each mailbox and manually reviewing the contents in the Zoom desktop app?
Can we export the contents of a mailbox?