[Exim] rate limiting

Hello,
besides smtp_ratelimit_* which only limit on one smtp connection, is there a way to limit a host to say, x number of connections per second/minute?
I find I can limit via ratelimit and smtp_accept_max* all I want, but a client can still send mail through the server as fast as can be by using a separate connection per mail, even if the server only allows a small number of concurrent connections.

Thanks,
Mike