>"Don't open any file attached to e-mail, from anyone, without first
>scanning the file using a good, current, anti-viral product."
That should be "Don't EXECUTE any file attached...". To use an already
installed program to open a received data file is not dangerous unless the
program is braindead (such as Microsoft Word with its macro-viruses). The
dangerous things are if you receive PROGRAMS and want to run them on your
computer.
>To follow his advice, should scanning be applied to the attachment
>before it is decoded from Mime, before the decoded attachment is
>unZIPped, or after it is unZIPped?
After decoding and after any decompression.
>And can PC-Yarn be configured to do this?
Metamail probably can.