🚀 go-pugleaf

I would like to configure a UNIX machine such that any mail sent to a certain
Internet-style subdomain address would actually just get "sent" to a certain
file, i.e., the complete message would get appended to a file.  For example,
assume my machine is "domain.com". I would like to set up a subdomain called
"subdomain".  Say someone sends mail to "fred@subdomain.domain.com".  I would
like it such that when that email arrived, the message would be intercepted
and appended to some file. This would be the case for _all_ mail sent to
"@subdomain.domain.com".  I would process the "append file" on my own.
 
Is this possible across UNIX systems?  How could it be done on the following
platforms:
          1) SCO UNIX v3.2.2 and v3.2.4
          2) SCO XENIX v2.3.4
          3) NeXTSTEP (BSD 4.3)
          4) MWC Coherent
          5) AT&T System V Release 4.x
          6) SunOS
 
Ideally, the same method will work on all UNIX flavors, but I am guessing
that things won't be that easy!  All suggestions/comments welcome, thanks!

Brian Dear /// brian@coconut.com /// Coconut Computing, Inc.