.em$ is Cheyenne Bitware file
Key Features: .EM$ File Extension
What is an .EM$ file?
The em$ file extension is associated with the Cheyenne Bitware fax and calling software for computer modems developed by Cheyenne Software, Inc. The .em$ file stores various data used for internal purposes of the Cheyenne Bitware.
Cheyenne Bitware seems to be obsolete product.