So your zimbraMailTrash/SpamLifetime is how you want it then, now re-read all references in this thread to zimbraMailPurgeSleepInterval.
To set:
zmprov ms server.domain.com zimbraMailPurgeSleepInterval 1m
Easier question: How many users does your system have?
The new default is 1m (capable of purging at least approx 1440 accounts a day).
1h is fine for smaller setups.
If you we're the
only account on the system then setting it to 1d would do what you want
