Files that contain the .efx file extension are most commonly associated with the eFax fax messaging software program.
eFax is a digital faxing application that allows users to send and receive fax transmissions via email or by using the online eFax Internet interface.
When a fax document is created by the eFax application, the file is saved to the user's computer with the .efx extension. These files can contain the body of the email that was sent via fax as well as any attachments that the fax may have included.
EFX files can be converted into PDF or TIF files using the eFax Messenger application.
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If you have additional information about the EFX file format or software that uses files with the EFX suffix, please do get in touch - we would love hearing from you.