How to restrict group mail ?

I saw on proc-mail archive that you
gave someone a solution to
how to make proc mail filter certain users
from mailing list (alias)

you told him to do the following thing

************
    :0
    * ^From: administrator
    ! (actual list of recipients here)

    :0
    | ( formail -t ; echo "You are not allowed to send mail to all_users" )
\
      | $SENDMAIL $SENDMAILFLAGS -t

******************

I followed those instructions, and it worked only partially

when I sent e-mail to the alias all_users from using administrator identity
through outlook 2000, it retuned the e-mail and said I was not authorized
to send e-mail to all_users, BUT
when I sent e-mail through Pine it worked beautifully,
I checked the headers of the message the recipients got
and found out that the "From:: field contained
"administrator(_at_)localhost(_dot_)localdomain"
but it should contain "adminstrator(_at_)myhost(_dot_)mydomain"
that means procmail changed the "From:" header.

can you tell me what can cause this to happen
and how to fix this problem
thanks in advance.