sieve setup. no svbin ?

[Voytek Eymont]

since moving/upgrading system I've noticed I no longer get sieve script
compiled, there is no dovecot.svbin created in
/var/vmail/vmail1/sbt.net.au/voytek at tld.au/sieve

what am I missing, how to check ?

also, looking at sieve.log, I see a lot of

May 31 06:32:50 lda(voytek at sbt.net.au)<1234><c4aVBfI98FzSBAAAyLbbsQ>:
Error: sieve: Failed to initialize script execution: Invalid
postmaster_address: invalid address `root' specified for the
postmaster_address setting

# grep root dovecot.conf
    postmaster_address = root

what should I have ?

# dovecot --version
2.3.6 (7eab80676)