Although I suspect that would also fail, the combination of a redirect and a reject might be worth trying. The sieve code would be something like
Code:
if header :contains ["From", "X-Mail-from", "Return-Path"] "xxxx.da.gov" {
redirect :copy "me@another.com"
reject "Message rejected because Invalid Email Recipient";
stop;
}
Not tested!
Possibly worth trying as the redirect may be processed at SMTP time.