Marco, > Is there a way to share this kind of information between Postfix instances? > I would really if you could share your personal experience on how to deal in > general with a scenario like this.
I've been using policyd for this, with a single MySQL backend. You can create a policy to match the specific recipient domains for which you want to limit, then associate a quota with that policy that limits (messages)/(unit time) by recipient domain. The postfix servers could all then use check_policy_service against policyd, and everyone would be receiving and updating the same counters. I have no idea how well this would work in your environment due to the extra overhead, but in practice it's worked well enough for me. Hope this helps, Steven
