Recipient rate limiting is not supported, not sure if this is technically feasible either to even consider it, given how much current and historically data that PowerMTA would need to store/have access to in real time, using the type of hardware customers tend to run on.
Assuming that you are receiving this after the RCPT TO command, is PowerMTA attempting to deliver to the next recipient there? Why not let PowerMTA just handle this normally, moving on to the next recipient and retrying that recipient later?
Have they told you specifically or are you seeing any trend there that indicates that receiving this error hurts your reputation. On the surface, seems like a simple error that is straightforward, and which will not negatively impact your reputation. What is the cause for concern when receiving this error? That would be good to know.
