File Extension MX2 File Format MasterCook file MX2 stands for MasterCook 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 setup new domain in exchange 2 Companies 1 Exchange I have installed Microsoft Small Business Server 2003 R2 but am unable to send and receive emails.