On 02/13/2013 06:16 PM, Jon Morby wrote: > So far I've been told > > its my DNS (but they can resolve the A record, just not the MXs) > there was a suggestion that IPv6 might be to blame and they either > can't talk IPv6 to our NSs or to our MXs - so we've dropped v6 from > some of the DNS entries .. but still they ignore the MXs and go > straight to the A
> Oddly though emails to fidonet.com <http://fidonet.com> work … just > not fido.net <http://fido.net> > > Now fidonet.com <http://fidonet.com> has no v6 in it's DNA currently > .. which is why we were looking at IPv6 issues (again) Could it be an issue with DNS response size ? Responses with MX and/or AAAA records in them are going to be larger than just A records. This may or may not be related to use of EDNS and/or queries over TCP vs UDP. However, it's not clear that such packets would be big enough to run up against regular network-path MTU issues, which makes me wonder if you might be the collateral victim of some half-arsed attempts to filter back-scatter of DNS reflection attacks. Keith
