One of our users is having trouble reaching an agency. He is getting email undeliverable messages after our exchange server tries and tries. Their admin says its a problem on our end. In the exchange logs it claims that we are probably blacklisted by their ISP or other intermediary. This makes sense to me since we are able to recieve emails from this agency but we cannot send to them. Anyone have any other input? Im getting a tad miffed that the admin there is just pointing the finger without bothering to do any work. We have no problems sending to any other agencies or individuals.