On 2012-06-05 07:29, Raymond Dijkxhoorn wrote: [..]
;; ANSWER SECTION: comcast.net. 358 IN MX 5 mx3.comcast.net. comcast.net. 358 IN MX 10 mx1.comcast.net. comcast.net. 358 IN MX 5 mx2.comcast.net.
;; ADDITIONAL SECTION: mx2.comcast.net. 6958 IN A 76.96.30.116 mx3.comcast.net. 358 IN A 68.87.26.147 mx1.comcast.net. 358 IN AAAA 2001:558:fe14:70::22
You are now only accepting IPv6 if all IPv4 fails? Or will AAAA records for mx2 and mx3 added later?
Though it can work, it used to be a really bad idea as there where a couple of SMTP systems (Communigate Pro being one of them I recall) which just failed when not seeing an "A" on an MX, this as they did not understand IPv6... There is bound to be other systems that are broken like that that will not failover to the secondary MX, as such, you might want to add an IPv4 address there too just in case. Greets, Jeroen