Problem:
When you’re migrating, and you see the new mailbox has standard folders in 2 different languages.
Or
You cannot change the default folder names to another language by using the /ResetFolderNames switch in Outlook
Solution 1
Use Powershell in the local server to correct this:
E2010/O365 : No name reset, when using Outlook.exe /resetfoldernames [Solved]