Did you setup a DNS server for your local lan 192.168.*.*? Looks like the name resolving and Reverse Name resolving is causing you problems.
Personally, I use a local DNS server to manage a xxxx.loc domain on a 172.16 IP range. It also serves rDNS requests to keep several packages happy that "require" valid responses to a rDNS request. I believe the smtpd deamon of postfix is such a program.