[exim] Exim SpamAssassin ACL to not check outgoing mails

Hi!
How to modify this ACL?
  warn    spam       = nobody
          add_header = X-Spam_score: $spam_score\n\
                       X-Spam_score_int: $spam_score_int\n\
                       X-Spam-Flag: YES\n\
                       X-Spam_bar: $spam_bar\n\
                       X-Spam_report: $spam_report

I need to not check outgoing mails from authencticated user system@???
Thank you for the help!