Dovecot LSA would pretty much have to implement full SMTP server functionality to be able to do this (although maybe it could get away with not doing queuing). I'm not really interested in writing an SMTP server. It would be much less trouble to change Postfix to work in a way that you want.
dovecot have lmtp, postfix have lmtp, so does quotas work in lmtp deliver ?
else one need to use postfix sql to dovecot dict to get used quotas :/
