Mail Bounced Instead Of Deferred – DNS Forward
I recently had a problem with my mail servers where messages received by my MX were bounced, rather than deferred, when the internal mail server the messages were destined for went offline.
This turned out to be because of my DNS configuration. The cause of the problem surprised me, because it was so decoupled from the mail setup. Hit the jump for the full story and solution.
Xen 3.2 Bridged Networking Explained by Experiment
There exists a lot of documentation explaining how to setup specific network configurations, but nothing that went through a complicated configuration in step-by-step detail. After a day of experimentation I figured out the exact symantics of the bridging configuration. This is still pretty non-advanced stuff, but I am attempting to explain it in detail to help make it clear to new users right from the start.