How Exchange Online automatically cares for your public folder mailboxes (via AutoSplit)

tonire Sorry for my late replay, It doesn't matter if the mailbox is serving hierarchy or not, you can check and compare the PF hierarchy on a secondary PF MBX with primary PF MBX by running that command twice Get-PublicFolderMailboxDiagnostics -IncludeHierarchyInfo check that article for more details.

It doesn't matter If you were on a PF coexistence since you are going to run that script several times during migration to sync any MEPF updates "add new MEPFS, delete non-existent MEPFs,...etc" to EXO, so for such an error "failed to resolve" I would start to check for that EntryId by running get-publicfolder & get-mailpublicfolder may be there's a discrepancy on the EntryIDs populated or even it's not a MEPF any more.

We are raising the quota to give space for the mailbox to be able sync the data inside to the target mailbox using the PFmoverequest created by the system, if that scenario recurred several times we would check the PFmoverequested if it was about to complete then we'll wait else we can remove that PFmoverequest and create a new one containing the largest PFs on that source mailbox to allow some space for the source mailbox without the need here to increase the quota.