To remove the Facebook folder from your IncrediMail folders list (along with any related features), simply follow these steps:
1. Open IncrediMail, click the 'Tools' menu and select 'Options'.
2. Select the 'Emails' tab, and click the 'Facebook Settings' button.
3. In the opened dialog click on 'Disconnect' and then uncheck the 'Show Facebook Folder' option.
4. Click on OK.