sieve works for one user, but not another?

[Mike Eggleston]

I have sieve working (except vacation) for me and I'm trying to
test the filtering rules (not vacation) on another user. It appears
that sieve is not working for that other user. Is there something
I've forgotten to turn on? Must I turn on sieve for each user?

Fedora Core 5
cyrus-imapd-devel-2.3.1-2.8.fc5
cyrus-sasl-lib-2.1.21-10
cyrus-sasl-2.1.21-10
cyrus-imapd-utils-2.3.1-2.8.fc5
cyrus-sasl-ldap-2.1.21-10
cyrus-imapd-2.3.1-2.8.fc5
cyrus-sasl-devel-2.1.21-10

Mike