[exim] How to deal with '<>' mails

Hello all,



I'm an exim noob and I'd appreciate some help.

We are trying to come up with a solution to prevent our servers from
accepting and forwarding/queueing mails with '<>' from addresses.

We are used as an outbound relay by a large number of clients and I am
trying to take into account that they

may be relaying ndr's out through us.

We don't want to blacklist any clients for sending invalid mail with no
from address on the basis

that the some of the mails may in fact be ndr's and not just junk.

I was thinking of simply denying such mails based on recipient
verification, but I'm not sure what the condition should look like for
this.. if anyone had any ideas they would be greatly appreciated.

Also I'm not a 100% sure that servers should be forwarding us on ndr's
without verifying the recipient,

am I totally incorrect in this thinking??



Thanks :-)