So the basic idea behind this is to permanently hold onto a users mailbox if they have left the company and we may need to review their mail at another time.
There is a requirement for the user to have an Archiving License with In-Place Hold assigned to his mailbox. At the stage of writing this, E3 is the only license available with the In-Place hold.
My client only has E1 licenses applied to their mailboxes
To work around this I have had my client agree to purchase a Single E3 License which we can move around to the mailbox we need to Archive
First of all go into Exchange Admin Center & select Compliance Management
Select the Plus button to Add a new in-place e-discovery & hold policy
Add a name as required. I have labelled mine Terminated Employee’s
Select Add and find the Mailbox you would like to Archive. Ensure the E3 License is applied
The Search query we ignore
Select the box to Place content matching the search query
and ensure Hold indefinitely
Now feel free to remove the mailbox