Re: [Exim] limiting relay based on sender address

> Is this a good idea?

No.

>Are there any potential problems doing it this way?

The first thing (well ONE of the first things) an _external_ spammer will
try is to set the sender domain to something that the server they are
testing is MX for, hence yuo will immediately become a big time spam relay.

> Basically, I want the system to be a 'good citizen' and not be a
> contributor to spam, and if someone uses it, I want it to be easy for
> victims to contact us to get the offending user punted off the system.

And when the sender turns out to be a hacked PC in Korea, you will do
exactly what about it?