Sophos researchers have spotted an active malicious spam campaign impersonating the DuoFax internet fax service, claiming that the recipient has received a fax:
You might not have a fax machine in your office or home, but you can’t help but be aware that some services and individuals inexplicably still continue to use this old technology. You may have had to send out a document on occasion, and not possessing a fax machine yourself, you might have resorted to using service such as DuoFax.
But don’t be fooled by emails such as these. Even though the sender’s email address has been spoofed, and the text contains no bad grammar, unasked-for emails should – as a rule – be considered dangerous.
In this case, if you do download and unzip the attached archive file, your suspicion should finally be raised by the fact that the file is an executable.
If you’re still not sure, you can always upload the file to an online file checking service such as VirusTotal – chances are one of the AV engines it uses to check files will identify it as malicious. In this case, it seems to contain a rogue AV solution.