Throttle outgoing mail by domain in exim
Solution 1:
I have found this thread on the exim mailing list.
They discuss different hacks and workarounds for throtteling including
- writing a shell script to manually sleep and deliver the messages (with
exim -M) - postfix as a "smarthost" which apearently can do what we want
- configuring a router that just sleeps for some seconds and then passes the message to the next router