On 29 Sep 2020, at 08:44, John R Levine <johnl(_at_)taugh(_dot_)com> wrote:
(There are already some IPv6 only ISPs and I expect this will become more
viable over time. Should they have to set up IPv4 tunnels or ALGs for
their "legitimate" customers so those customers can still send email to IPv4
servers?)
No, they need a fixed IPv4 address with an MX so people on IPv4 servers can
send mail *to* them. As we've said a few dozen times already, one mail
server on one IPv4 address can handle a whole lot of mail for a whole lot of
people, both inbound and outbound.
The usual word for one-way mail to which one cannot reply is "spam”.
And if you have a IPv6 address that is reachable it is not “spam”. Out bound
address do not have to
match in bound addresses. Remember this is delivering email to legacy
addresses who may well end up
having a smart dual-stacked host for outbound traffic to workaround not having
IPv6.
Regards,
John Levine, johnl(_at_)taugh(_dot_)com, Taughannock Networks, Trumansburg NY
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Mark Andrews, ISC
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