If you get an error of "Language was not updated to prevent an email folder name conflict" when trying to change your language, it means that the user has a custom email folder with the same name as one of the default email folders, but in the language they're attempting to change to.
For example, if the user is trying to change their language to Portuguese (Brazil), and they're getting that error, it means they have one of more custom folders in Portuguese named Inbox, Deleted Items, Junk Email, Drafts, or Sent Items.
In order to change their language, you'll need to delete or rename the custom folders to something that does not match the same translation string we use when you change your language to Portuguese.