The original message was received at Tue, 28 Jul 2015 00:59:30 +0800 from [117.182.158.19] ----- The following addresses had permanent fatal errors ----- <dev at openvswitch.org> ----- Transcript of the session follows ----- ... while talking to openvswitch.org.: 550 5.1.2 <dev at openvswitch.org>... Host unknown (Name server: host not found)