Sieve - Reject - Backscatter worries

[John Thomas]

I would like (for convenience) to use Sieve to reject certain messages, 
but do not want to send backscatter.  I followed
http://www.delouw.ch/linux/Postfix-Cyrus-Web-cyradm-HOWTO/html/
but am using Simon's latest Cyrus RPM.  I only have a few users.

If I "reject" with sieve, will I send backscatter or will the sending 
server get the slap in the face?