We have set up a small install of zimbra. Some of our mails are getting rejectec and I believe it has to do with the inverse lookup check that some servers do.
From the admin gui I can se that there are a couple of message that stay in the cue. When I check the error it is usually related to the name of the sender and its IP (sorry I don't have access to the exact error rigth now).
Our configuration is very basic. We are behind a firewall provided by our ISP which we do not have much access to. In our local network there is a zimbra server and a DNS for local computers.
Since I have to use (right?) the ip of the router as mail server in our external DNS (provided by the company we got our domain from) I do not know how or if I can configure the system so that some of the mail is not rejected.