Ken, You are correct, resolve.conf does list my isp's dns 250.171.3.65 which is qwest. The internal windows workstations also point o the isp's dns server. Can I setup a cashing dns server on the mail server itself?? PS: I just wanted to say thanks to everyone who has helped me so far. -jr Ken Price wrote: > Jason, > > This has nothing to do with AUTHORITATIVE dns. I'm speculating this > is a problem with your choice of RECURSIVE (caching) name servers. > Realize, however, that without being on the box and looking at your > configuration, all I can do is speculate. > >> Mail .medvoice.com actually resolves to the mail server inside >> through port forwarding. > > Very typical. > >> It's not really named that just everything going to the mail ports >> ends up there. > > Understood. Again, very typical. > >> Would DNS still be an issue for sending internal mail. > > Maybe, maybe not. It depends on your internal network setup and where > your server and workstations sit respective to each other. What's in > your server's /etc/resolv.conf file? On your windows workstation, > from the command prompt: ipconfig /all ... what "DNS Servers" are > listed here? > >> I ran top during one of these unresponsive email spats and noticed >> that there are no smtp processes listed. > > That just means there's no Postfix process in the busiest 20 or so > processes. Use the command "ps -aux" for a more complete process > view. That also means it's very unlikely your server is overloaded or > reaching process limits. > > When someone initially connects to your mail server, typically the > first thing your mail server does is a reverse IP lookup on the person > connecting. Then, depending on your setup, it could also query a > number of RBL sources (Real Time Black Hole Lists) to see if the > sender is a known spammer. The more stuff that is done on that > initial connection, the more DNS lookups your server has to make and > the longer it takes to return the "OK" 220 prompt. That's why I'm > speculating this is a DNS issue. If my hunch is correct, your > /etc/resolv.conf will point to your ISP's recursive (caching) name > servers. Rarely do they perform well since they're shared amongst > hundreds/thousands/millions of users. For performance reasons, > you're better off running at least one caching name server of your own > inside your network - even on the server in question. While this is > only speculation on your problem, these methods also lean towards > "Best Practices" and are simple to implement. > > -Ken > > > > > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos >