EFX files are compact FAX files of the software eFax.
eFax stores received faxes in this format, among other things, which can be viewed with the free eFax Messenger. Efx files can be used for local archiving or forwarding of faxes.
eFax by j2 Global Communications is a paperless fax service that gives you your own local fax number. Incoming and outgoing faxes are sent or received via an e-mail or mobile phone number to be specified. The messenger is only available for Windows, but the fax service itself can be used from any system.
Most often resolving problems with opening EFX files is very simple. Just install an appropriate program that supports such files. All of the listed programs support EFX files, but may vary in offered function and purpose. Some programs may be capable only of viewing contents of EFX files or offer file conversion options, but may not be capable of editing such files.
It is possible that although a compatible program has been installed on user’s system, it is not used by the system to open it. This may happen because no default application was associated with this type of files. To associate EFX files with given application, select "Open with" from drop-down menu (accessed by right-clicking on the file). Then select from the list the program or application you want to be used to open this type of file. If the eFax applications is not on the list, select "Browse" option in order to manually locate the directory where eFax has been installed.
Sometimes problems with opening EFX files may not lie with the application itself, but can arise due to other causes, such as: