File Extension SMF File Format Fax document (SMARTFAX) SMF stands for Fax document (SMARTFAX). 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 Fax machine keeps saying out of memory and poor line connection HP all-in-one 6500 fax error 350 Can you "read" a fax or email/attachment with a program or 3rd party tool?