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

Select Finish

Now feel free to remove the mailbox