You can't actually do nothing with that. Folder names and their initial structure inside the Mailbox are determined by Scalix during mailbox creation. Thunderbird is only intended to manage mail messages : therefore the only folder it automatically translates in the local language is the "Inbox" IMAP folder (in italian it gets translated into "Posta in arrivo").
There is also a thing you should take care of : when connecting using Thunderbird in IMAP mode Mozilla creates a new folder for deleted items named "Trash" (you can see it after a successful configuration of Mozilla and then try open the same account using Webmail). If you want TB, Outlook and Webmail to share the same deleted items folder (which in Scalix's mailbox is named exactly "Deleted Items") you have to perform a simple configuration on Thunderbird.
In thunderbird 2.x do the following:
- Tools -> Options -> Advanced
- Click on "Configuration Editor" button (lower right)
- In the "Filter" field enter "mail.server.server#" where "#" is the number of your configured account (by default "1" is for the local folders, "2" is for the first account, "3" for the second and so on). So if you have only one configured account in TB you have to search for the value "mail.server.server2"
- In the filtered list look for a key value named "mail.server.server2.trash_folder_name": if it's not there create it by right clicking in the list, choose "New -> String" and enter the name of the parameter value "mail.server.server2.trash_folder_name" (without quotes); immediately after you are prompted to enter the value to assign to this parameter : enter "Deleted Items" (without quotes and honouring capitals).
- Save all and restart TB
After this operation TB uses the same "Deleted Items" folder as Scalix's webmail and you can now remove the "Trash" folder which is no longer needed.
All other folders like "Contacts", "Notes", "Appointments" ... have simply no meaning for Thunderbird as it would expect to find mail messages there ... but there are not.
You can find a complete tutorial here: http://kb.mozillazine.org/IMAP_Trash_folder