If you ever want to export / import a mailbox use the below

1- You need to set a role assignment to the user

New-ManagementRoleAssignment –Role “Mailbox Import Export” –User AD\Administrator

2- To Export Run the following command

New-MailboxExportRequest -Mailbox "SourceMailbox" -IncludeFolders "Namethefolder" -FilePath \\servername\c$\mailboxexport.pst

3- To import run the following command

New-MailboxImportRequest -Mailbox "NewRoomMailbox" -IncludeFolders "namethefolder" -FilePath \\servername\c$\mailboxexport.pst


For Example, the below exports calendar items from one Mailbox to the other

New-MailboxImportRequest -Mailbox "OLDRoomMailbox" -IncludeFolders "#Calendar#" -FilePath \\servername\c$\meetingroomcalendat.pst

New-MailboxExportRequest -Mailbox "NEWRoomMailbox" -IncludeFolders "#Calendar#" -FilePath \\servername\c$\meetingroomcalendat.pst