I recently encountered an issue which I have seen before but never this bad and more commonly with Public Folders. My customer had a 50GB mailbox that also had an archive mailbox. The mailbox would get so far and just stall and never complete.

So I tried all of some of the usual methods to repair the mailbox to no avail.
Repair the mailbox with PowerShell & Migrate the mailbox to another Exchange database

So we asked the customer could we review the mailbox and found thousands of folder in the format of 16/04/2019. Exchange does not like / , Exchange normally sees / as the top of the information store. So my first attempt to resolve this was powershell and could not seem to crack it. Thanks to my colleague Mark Doyle  ,We resolved this issue with an Outlook Macro.

So if you ever encounter this unique issue , Please follow these steps.

1. Browse to the Outlook Trust Center
   
2. Macro Settings, Select Notifications for all Macros
   
3. Press Alt + F11 to open Visual Basic
   
4. Double click “This Outlook Session” under Microsoft Outlook Objects
   
5. Paste  this TEXT below into the window
6. Click on the folder or inbox that you want , And run the Macro
7. Input character we want to replace in this case will be /
   
8. Then select . as the replacement character
   
9. Finally task complete
   

Final Comment

This is in no means an enterprise solution and I asked Microsoft for help and didn’t get anywhere. Once we removed the / , We could see when checking get-moverequeststatistics (mailbox) , that it was getting past the ‘create folder hierarchy’ stage in a mailbox move. And we did not need to tell our customer , Sorry this mailbox cannot be migrated!