Office 365 Export Public Folders and Import into a Resource Mailbox – Combat IPM_Subtree issue
Not really to get into the controversy of public folders in this post however in O365 you can have ‘Resource’ mailboxes that can be made up of either room ore equipment
Exporting the data from public folders into PST is somewhat as straight forward as you would expect
Do this on a per Public Folder Basis.
Click on File ->- Import and Export
Select option Export to a file
Select ‘Export to PST’
Select the Public folder calendar that you want to export
Specify the PST file location and choose Allow duplicate items to be created
The next step is once you have created your corresponding Resource mailboxes pick a user in O365 and give them Full Access Rights. You will then need to add the resource mailboxes to the individuals Outlook and then import the PST in a very specific way
If it is not imported correctly then the data will be placed inside of a IMP Subtree folder rather than the calendar itself

Correct Import
Now that we have the local resource mailbox added we can ……
– Flick to Calendars
– Select the one we are concerned with i.e ‘CEO Meeting Room’
– Go to File-Import PST
Select the following options

Once you go through the rest of the menu, you shall see the items drop into the calendar correctly