Overriding dovecot.conf from Userdb Extras

[E.B.]

> > I thought I read that anything from dovecot.conf can be overridden in a
> > userdb lookup. Or a passdb lookup with "userdb_" prefix.
> >
> > But I tried for fun change log_path but it never worked. Is that because
> > logging is special, already started logging before it comes to the
> > passdb/userdb lookups? So are there some dovecot.conf settings
> > that cannot be overridden?
>
>
> To my understanding only these extra parameters can be tweaked through the
> userdb/passdb:
> http://wiki2.dovecot.org/PasswordDatabase/ExtraFields
> http://wiki2.dovecot.org/UserDatabase/ExtraFields (+ mail and quota_rule)

Quoting from your second link:  "It's possible to
override settings from dovecot.conf" (quota rules
being a common example, yes).  

I've successfully overridden a few different
dovecot.conf settings, mostly for lda and sieve,
but also mail_debug from 10-logging.conf.  So
it does work to override *some* settings from
dovecot.conf -- but there seem to be a few like
log_path that are immune to overrides I guess.