How to Open a .P7s File. A P7s file is a digitally signed message designed to be opened in Microsoft's Outlook application.

How to Open an MSF File. A file with the MSF file extension is most likely a Mozilla Mail Message Index file. The MSF file type originated with the Netscape Mail application, which has since been ...

If 7-Zip cannot open an archive or compressed file and you see Cannot open file as archive error message, here's what you can do.