Writing an ASP file to pickup folder for SMTP

[Fox]

Forgive me for asking this here.
I know it is a stretch topic-wise,
but there is only one SMTP group
and very little in the way of anyone
answering anyone else.

I am writing a file to disk using ASP.
This file is to be written to the SMTP
pickup folder. It includes the correct
basic headers and works. The headers
include

X-sender
X-receiver

Can anyone tell me where to get info on how
I go about sending an attachment this way ?

Thanks,
Fox