EFax

eFax is an internet fax software owned by J2 Global. J2 Global was founded in 1995 as JFAX.com. eFax Messenger is software which can send and receive image files in the proprietary .EFX file format.

File Identification
J2 Global's original JFAX service used a file format based on the TIFF-F format with a .JFX extension. Also known as J2 Messenger.

Version 3 & 4 of the .EFX file format is proprietary and begins with hex values then 2 bytes of unknown values then 6 bytes.

Version 5 is unknown.

Software

 * Current Version of eFax Messenger
 * Archived version of eFax v3 (Mac) & v4 (Windows)