I have an older HP Pavilion Laptop with Windows 10 installed. Recently, when I try to delete about 70 old emails in the program I get an error message dialog box "An unknown error has occurred" and I can't delete any of these message. I also cannot open these message either. New emails don't seem to be affected. This has happened before but the problem went away but happened again.  Any idea what is the cause and how to fix it?

Richard J. Cassese