The file extension UNK is commonly referred to as an Unknown File Type and can originate from an email program or it can be downloaded from the Internet. UNK file can be related to a variety of different programs and applications but will appear with the UNK extension if the file cannot recognize any program on your device which will support it. This extension may also appear if the file has become corrupt during the transmission process.
UNK stands for UNKNOWN and the files are a proprietary file format which is associated with the program that created the file. UNK files have been commonly linked to Microsoft Mail, which is very similar to the Outlook mail client. In this case, the contents of a UNK file will contain data related to email messages, which include text, hyperlinks, HTML, and other elements typically used when composing an email message.
UNK files can also contain data related to a wide variety of programs and applications. This means the file can include text, multimedia content, spreadsheet data, graphics, images, programming language, and other types of information. UNK files can contain malicious content which is intended to harm your PC or spy on your computing activities. For this reason, you should also exercise caution when open UNK files.
How to Open UNK Files
If you have received a file with a UNK extension as an email attachment and it originates from a trusted resource, the file either does not recognize any programs on your PC which support it or it has become corrupt during the transmission process. When files are transmitted over the Internet and the process is not successful, the files will automatically be converted to a UNK extension when they are not transmitted properly over a network.
If the above description of the UNK file is valid, you can attempt to open the file using Microsoft Mail on a Windows-based PC. If the UNK file has become corrupt, then you can download an application that is capable of repairing the file so you can open and read the contents. Programs such as FileCure and others are available for download on the Microsoft download website and sites such as CNET or Softpedia.
If you do not know the origin of a UNK file, it is wise to first try and determine what program created it. If you use Windows, right click on the file and then choose Properties from the drop-down menu. In the Properties window, click on the Details tab to see if there is any information associated with the file. If you use Mac OS X, right click on the file and then choose Show Package Contents to see if you can learn more about the origin of the file.
You can also try using a file reading program designed to read a wide variety of file extensions. There are a number of free file reading programs available for download on the CNET website.
If you are unable to determine where the UNK file originated, you should avoid opening the file. UNK files that have no known origin have a high probability of containing malicious content and in this case it is better to delete them.