[exim] rate limit for maximum outgoing emails to mail-relay

Hi!

We have a application, which creates many emails. Notifications from a
ticketsystem to the subscribed users for each ticket on changes, or
something else.

We use gmail suite as our email-provider, and gmail has some
send-limitations. So, if many tickets are created as a bulk, many many
emails are created from the app, and the mailserver blocks the sender
for 10 minutes. Most of the created emails go to the error-mail-queue
from the app and must be resent manually.

There is a workaround on the vendor-site, because the app itself cannot
handle to ratelimit the sent emails.

The workaround is, to put a local mailqueue in between, which ratelimits
the outgoing message-count.

I want to realize this with exim4, if there is a possibility to set a
hard limit for a specific smart/relayhost for outgoing emails. The app
can send as much emails as used, and the mailserver queues them all and
send them to gmail-relay-host in packages of 80 mails per minute. Not more!

How can i handle this with exim4?

thank you

jakob