On Wed, Dec 21, 2005 at 04:13:04PM +0100, Stig Venaas wrote:
On Wed, Dec 21, 2005 at 04:08:16PM +0100, Florian Weimer wrote:
* Gert Doering:
So if I understand this correctly, having a v4-only backup MX should solve all problems commonly experienced?
As far as I know, the primary MX needs an A record (to satisfy Sendmail), and there needs to be a MX which has an A record only (and no AAAA or A6 record; this is done to satisfy Exim installations). My initial question to this list was whether if you can do this with just a single IPv4 address, and still prefer IPv6 over IPv4 (assuming that IPv6-capable hosts prefer IPv6 hosts over IPv4 hosts if they have the same priority).
At least at uninett.no this is done with only one IPv4 address. The primary MX has both A and AAAA, and the secondary is only A, but with same IPv4 address as primary. Well, you can check mx's for uninett.no yourself.
I know several sites that have both A and AAAA for all MXs. It doesn't sound safe to me, but I assume it can't be that problematic then...?
Like Gert and Jeroen, we do that, and have not had complaints of failed or problematic email (and have done it for a long time). That's on a domain handling maybe 100K mails a day. -- Tim/::1