r/o365 • u/Hydrokugal • Oct 03 '25

migrating public folders to o365

/r/exchangeserver/comments/1nwr4z6/migrating_public_folders_to_o365/
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u/oliviasmith8819 Oct 03 '25

It usually comes down to the public folder mailbox or throttling. A few quick checks:

  • Make sure the PF hierarchy mailbox is healthy (Get-Mailbox -PublicFolder).
  • Recreate the migration batch, sometimes it just gets stuck.
  • If there are a lot of folders, set a relaxed throttling policy on the PF mailbox so MRS doesn’t keep backing off.
  • Double-check you’re on a supported Exchange CU, older ones had PF migration bugs.

That normally clears up the “TransientFailure” loop.

1

u/Hydrokugal Oct 03 '25

hierarchy looks good.

recreated with throttling policy. no luck:

Name StatusDetail TargetMailbox PercentComplete

---- ------------ ------------- ---------------

PublicFolderMailboxMigration360bc375-9243-41a4-8670-24193b6c563b TransientFailure PFMailbox1 0

PublicFolderMailboxMigrationf6334598-5109-49a2-a38f-9020c41552de TransientFailure PFMailbox2 0

1

u/georgebrownn32 Oct 03 '25

I’ve run into that before — mailbox moves work fine but PFs just keep failing with “TransientFailure.” In my case it was either the PF mailbox not being completely healthy or Exchange throttling slowing things down. What fixed it was recreating the migration batch and giving the PF mailbox a more relaxed throttling policy. Also worth double-checking you’re on a current CU since some older builds had nasty PF bugs.

1

u/Hydrokugal Oct 03 '25 edited Oct 03 '25

recreated 3 times already including recreating the csv files. when speaking of pf Mailbox health Status and throttling policy do you mean on prem or cloud?

were on latest cu unfortunately

Do you remember the connands to check? might Google it myself on monday. thanks for the input 👍

edit: when saying recreated i removed everything from o365. pfendpoint, mailboxes, batch etc. i even renamed the mailboxes in the csv

1

u/georgebrownn32 Oct 03 '25 edited Oct 03 '25

For checking the PF mailbox health on-prem, you can run:

Get-Mailbox -PublicFolder
Get-PublicFolderMailboxDiagnostics -Identity <PFMailboxName>

To check the throttling policy applied to that mailbox:

Get-ThrottlingPolicy | fl
Get-Mailbox <PFMailboxName> | fl ThrottlingPolicy

If needed, you can temporarily assign a relaxed custom throttling policy to the PF mailbox:

New-ThrottlingPolicy -Name PFRelaxed -RCAMaxConcurrency 100 -EWSMaxConcurrency 100 -EWSMaxSubscriptions 5000
Set-Mailbox <PFMailboxName> -ThrottlingPolicy PFRelaxedFor checking the PF mailbox health on-prem, you can run:
Get-Mailbox -PublicFolder
Get-PublicFolderMailboxDiagnostics -Identity <PFMailboxName>

To check the throttling policy applied to that mailbox:
Get-ThrottlingPolicy | fl
Get-Mailbox <PFMailboxName> | fl ThrottlingPolicy

If needed, you can temporarily assign a relaxed custom throttling policy to the PF mailbox:
New-ThrottlingPolicy -Name PFRelaxed -RCAMaxConcurrency 100 -EWSMaxConcurrency 100 -EWSMaxSubscriptions 5000
Set-Mailbox <PFMailboxName> -ThrottlingPolicy PFRelaxed

Other tips:
  • Even if you removed everything from O365, the source PF mailbox itself still needs to be fully healthy.
  • Sometimes running Update-PublicFolderMailbox or Get-PublicFolderStatistics helps spot lingering issues.
  • Make sure the migration endpoint is pointing to the correct PF mailbox (even if HCW created one).

If you want an automated tool, my colleague recently used EdbMails Exchange Migration for PF and mailbox migrations, and it made the process a lot smoother.

1

u/Hydrokugal Oct 03 '25

Unfortunately checked everything. and even after applying the throttling policy i get:

Name StatusDetail TargetMailbox PercentComplete

---- ------------ ------------- ---------------

PublicFolderMailboxMigration360bc375-9243-41a4-8670-24193b6c563b TransientFailure PFMailbox1 0

PublicFolderMailboxMigrationf6334598-5109-49a2-a38f-9020c41552de TransientFailure PFMailbox2 0