File Extension HOL File Format Microsoft Outlook Holiday file HOL stands for Microsoft Outlook Holiday file. This was last updated in March 2012 By Margaret Rouse Browse File Extensions Alphabetically: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # Ask a Question. Find an Answer. Ask your peers a question about this file extension. Ask a Question Microsoft Outlook 2007: Deleted folder Outlook 2003 - sharing specific types of appointments Can I locate .PST files in Outlook and verify the associated profile?