[exim] simple question about rate limiting

Hello everybody,

I've been using Exim for years now and I'm very happy with it. There's
one problem that I don't know how to resolve though...

I have a program that generates emails at night and calls exim directly
(on the same host) to deliver those messages. The problem is that some
receivers rate limit their incoming SMTP connections to 30 messages per
minute and reject anything over that.

How do I limit my outgoing rate per host? I've been reading about "ratelimit" but
I'm not sure if it applies in this situation. Also, I probably want the
outgoing messages that are over the threshold to be queued until the
they can be sent.

For example, if I define the outgoing rate to be 30 messages per minute
for a host, then provided 30 messages have already been sent in this
minute, messages 31 and up are queued until this minute is over. Then the
next 30 are sent and so on. In other words, I don't want my messages to
be rejected if I've reached 30 messages per minute.

Thanks for any suggestions,
Sergei