qmail problem

hello to all, I have a great problem with qmail.
I have configured qmail with fetchami and qmail-masq (package developed in
Perl to mask mail's address: when a user sends an email to another external
user to my domain, the direction of the sender is masked with an real
address of mail that exists on Internet, because my domain is fictitious).
When the email goes from a user to another user and both are on my
fictitious domain not is masked (It is obvious).
In order to obtain to this and mask as much the sender's address as the
return path with the previous package it is necessary to make the following
changes:
1) file tcp.smpt:
   127.:RELAYCLIENT="@fixme"
2) file virtualdomains: fixme:fixup
3) add a file in the directory alias: qmail-fixup-default with the following
line
   | qmail-inject

It work fine, but I have noticed that when I send a message to more of an
external user, the message is sent so many times as usuary I have added,
arriving at the adressee so many copies as adressees I have put.
Somebody knows like solving this problem, thanks.