I have a client running Red Hat Enterprise Linux v4 for web and email services. Their accountants have just implemented Exchange 2007 on Windows Server 2008, and have ipv6 enabled.
My client can send the accountants emails without issue. Unfortunately, when the accountantd send a message to my client, DNS resolution fails in ipv6, but does NOT fall back to ipv4. The accountants' tech guy says:
> > It seems our server can ping enterprise.xxx.net.au,
> > However when I do a wireshark capture and send an e-mail the DNS resolve seems to fail.
> > I think this is because your server is responding Server Failure for your AAAA (IpV6)
> > record, and as we are using exchange 2007 and Server 2008, ipv6 name resolution is
> > supported and enabled by default - and because it is returning failure instead of missing
> > record, exchange doesn't move on to ipV4 (while windows does).
Our DNS is handled by PlanetDomain, with only provides ipv4, so my guess is that something needs to be done by the accountants on Windows 2008 and/or Exchange 2007 to allow them to send out emails to my client's server. Alternatively, perhaps we need to make a change at the RHEL end.
Has anybody got any suggestions as to what to try?