When a license is removed, the mailbox is deleted (or is it just unlinked…). If you need to keep the data, convert the mailbox to a shared mailbox before removing the license.
I'm still not 100% confident about the mailbox not being deleted when you change the license… So I always pick a test user first, check it's mailbox contents before making changes (or check it's mailbox size in the Exchange properties), and then check again afterwards. At least if I know that I've done it before, then doing the same thing again will produce the same results.
My experiences: (all good so far)
Following experience is from changing an Office 365 for Students license to Office 365 for Faculty (June 2016): If you add a new license as an additional, then it will not delete the mailbox. However when you assign a new license, it will immediately say “We are preparing a mailbox for this user” - which is pretty scary! But I have confirmed it does not delete the mailbox, everything is still there. (of course don't take my word for it, do your own tests first! also check the mailbox size before and after, to be sure)
Following experience is from changing an Office 365 Business Premium license that had expired, to a new Office 365 Business Premium license purchased under a different model (ie the exact same license type, but a new instance of the license) (June 2016): It would not let me have both licenses assigned at the same time. But I in the 365 Portal, I could untick one license and tick the other, and then click Save, and the mailbox was not deleted.
Following experience is from changing an XX to XX (November 2016): Selected multiple mailboxes, then in the “Bulk Actions” panel, “Edut product licenses” > “Replace existing product license assignments”, set the new license to “On” (note the previous license was already changed to “Off”) and clicked “Replace”. Then it said “We are preparing a mailbox for this user” but after a while everything appeared normal, and the mailbox size for the user was around 4GB like it was before making changes.
Not all licenses support Overview of shared computer activation for Office 365 ProPlus - Office Support|Shared computer activation]]. The license needs to include “Office 365 ProPlus”.
Which Office 365 subscriptions include shared computer activation?
Any SKU that contains Office 365 ProPlus will be eligible for shared computer activation. This includes the following SKUs:
- Office 365 ProPlus
- Office 365 Enterprise E3
- Office 365 Enterprise E4
And all equivalent Government and Education SKUs are also included. Project Pro for Office 365 and Visio Pro for Office 365 also include shared computer activation.