So after several Exchange migration projects I have seen this a couple of times.
The names of the system folders in a mailbox (such as Inbox, Sent Items, and Draft etc) are in the wrong language or corrupt.
Since I Live in Norway I’ve got costumers that want them in Norwegian. like “Innboks” and not “Inbox”.
This can off course be changed with Powershell.
You can check the settings for an specific user:
Or check it for all users:
Get-Mailbox | Get-MailboxRegionalConfiguration
When you want to change the language for a spesific user to norwegian:
Set-MailboxRegionalConfiguration -Identity email@example.com -Language nb-NO -LocalizeDefaultFolderName:$true
or maybe you want to change all users to have English language:
Get-mailbox -ResultSize unlimited | Set-MailboxRegionalConfiguration -Language en-US -LocalizeDefaultFolderName:$true
Its possible to change / set timezone and date as well.
for more info check the following links