Forwarding hosts in mail addresses

[MILLER@VAX.CAM.NBS.GOV]

Apparently a number of mailers will accept the following syntax:
  @FORWARDING_HOST:USER_NAME@HOST.DOMAIN
meaning that you want to send mail to USER_NAME@HOST.DOMAIN
but send it via FORWARDING_HOST.  The point presumably being
that the local host doesnt know about HOST (ie doesnt have
the full domain service running), but FORWARDING_HOST will 
be able to figure it out. 

This works on suns and even the EXLAN mailer on vax/vms
(with a little syntactic sugar).  However, the LM chokes on 
the initial `@'.   Does anybody know how to make this work,
or an alternate syntax?

Background: Our vax can get to internet. we communicate with
the vax using DNA. We want to get TCP/IP (which would obviously
solve all this, or at least change the problem set), but not
this FY.  What I want to do is send mail on internet directly from
my comfortable LM, even if I've got to kludge the address a bit.
Currently, I've got to log onto the VAX to send it.

			Thank you
			Bruce Miller
			MILLER@VAX.CAM.NBS.GOV