After migration, Outlook folders such as Inbox or Sent Items appear with a different and incorrect language.
This can be because folders upon migration are initially created by the client using the client language settings. So if the client language is French, it retains the French language for folder names with any subsequent client used which may have a different language itself.
There are three possible resolutions:
1) Run Outlook.exe via the run command using the /resetfoldername switch. For example: Outlook.exe /resetfoldernames
2) Re-migrate using the correct language settings
The third resolution applies only when migrating to Exchange 2007.
3) In Microsoft Exchange Server 2007, you can specify the language preferences for a mailbox, in order of preference, with the Languages parameter by using the Exchange Management Shell and the Set-Mailbox cmdlet. E.g.: Set-Mailbox -Identity "User" -Languages "fr-FR"
This MS Technet article provides details: http://technet.microsoft.com/en-us/library/bb310757.aspx
This Microsoft Kb article provides further information: http://support.microsoft.com/kb/188856