Blocking MX query

Masataka Ohta mohta at
Wed Sep 5 03:40:30 UTC 2012

valdis.kletnieks at wrote:

>>> Have your desktop MTA configured to relay through your smarthost with smtp
>>> auth?  Howtos for doing this on sendmail, qmail, postfix etc are over a
>>> decade old now.
>> What if, your home is also behind NAT or blocked port 25?
> Weren't you the one who a few weeks ago was advocating more NAT rather than
> deploying IPv6?

NAT, here, means dumb NAT. With most, if not all, pseudo ISPs using
NAT, you can't expect port forwarding services.

While ISPs in the future should use not IPv6 but NAT with fixed
IP addresses and sets of port numbers assigned to their customers,
keeping the end to end transparency, it does not solve the
problem of blocked port 25.

Note that IPv6 do not solve the problem of blocked port 25, either.

						Masataka Ohta

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