Enabling autoexpunge for mailboxes created by sieve rules

Hi everyone. I have global sieve rules that can create mailboxes automatically by using "fileinto :create some/mailbox/that/does/not/exist". The emails are delivered to dovecot using lmtp and I can see the mailboxes created just fine. Is there a way to configure all new mailboxes created by those sieve rules to automatically set to autoexpunge after 15 days ?

I tried this , but it did not work.

namespace { type = public separator = / prefix = mypublic/ location = maildir:/var/spool/vmail/dovecot/mail/ subscriptions = no list = children mailbox * { autoexpunge=15d } }

plugin { acl = vfile }

# dovecot --version 2.3.15 (0503334ab1)

Thanks!