First – I believe the the field where it says "unknown" is a reverse lookup of your IP address.
If you type: host xx.xx.xx.50
Do you get a result? If not, you may need to talk to your ISP about setting up your reverse DNS (you control your DNS, but they control your reverse lookups).
As for your second question, that’s more difficult to resolve. Check out Joe’s response to this post:
OK my rdns has been and is good in that:
host xx.xx.xx.50
50.xx.xx.xx.in-addr.arpa domain name pointer vps.examplehost.net.
So it must be something else.
I looked at the link your provided and at the link in that link that joe provided and see something that might be the issue.
My VPS has an IP of xx.xx.xx.01
My virtual host on the VPS has a dedicated IP of xx.xx.xx.50
The Virtual host doesn’t use a mail server at xx.xx.xx.50 because it is using the VPS’s install of postfix so all mail is actually coming from xx.xx.xx.01
I wish edit worked but truthfully I would rather see Joe and Jamie working the software than on some forum install so I guess this is just a rant to ingore. Move along