[GLLUG] ipv6, privacy addressing, and mail servers.

[Tim Woodall]

On Thu, 22 Nov 2018, Andy Smith via GLLUG wrote:

> Hi Tim,
>
> On Thu, Nov 22, 2018 at 08:41:59AM +0000, Tim Woodall via GLLUG wrote:
>> The target mx in question is trying a reverse lookup, that is failing,
>> and then the mx is temp-failing my email.
>
> You cannot expect to send an email in today's Internet from an
> address that has no reverse DNS. This goes doubly for an IPv6
> address because from the start receivers tend to be more strict
> about standards for mail from IPv6 addresses. You should not be
> putting publicly-accessible Internet servers on privacy addresses.
>
An outbound mailserver doesn't have to be publicly-accessible. In this
case it also handles inbound.

Gmail, despite websearches suggesting it requires reverse dns on the
sending ip, doesn't seem to care so long as the ehlo is good.

>> What is the 'correct' behaviour?
>>
>   and configure your MTA to only ever use that address. Then add
>
There's always an easy answer :-) As this server also does inbound, I've
just configured it to use the fixed address. I should have thought of
that...

(just need to check ipv4 is still ok...)

Thanks,

Tim.