Licensing Exchange Online Shared Mailboxes

what happens it that mailbox is converted and the license is removed? Do I receive an email or alert (tenant admin)?   Does it fail?  

TR: If you convert a mailbox to a shared mailbox and it has more than 50 GB, you won't be able to send messages from that mailbox until you license it. I suspect you won't be worried about this if the mailbox is for a departed employee.

All of our users have Archives.  How does the archive change when converting to a shared mailbox and removing the user license?  Will I receive an alert or email? Does the archive get removed? 

TR: The archives stay in place. Microsoft doesn't enforce the licensing requirement on archives just yet, AFAIK.