I think I may have gotten a bit confused during this discussion. Could you clarify the following for me: Is it possible to automate the migration of mailboxes from a P1 plan to an E3 plan?
The discussion of using the Outlook client to manually move mails across makes it seem this is the only way... Is it still possible to use a .CSV import, or a perform a Cutover migration as mentioned here: help.outlook.com/.../ms.exch.ecp.emailmigrationwizardexchangelearnmore.aspx
I don't mind if I have to re-create a .csv for an automated import, but manually moving 50 mailboxes of between 1-18GB of mail isn't really a feasible plan.