Alessandro Vesely writes:
On Sat 30/Jul/2016 14:30:18 +0200 Sam Varshavchik wrote: > Matus UHLAR - fantomas writes: >> On 29.07.16 06:48, Sam Varshavchik wrote: >>> Courier should accept postmaster@[ipaddress], where ipaddress matches >>> the connection's IP address. It won't accept any other IP address.That means ipaddress matches the /local side/ of the connection if the mail address is a recipient, right?
You don't know who the recipient is until you check the domain.
>> what about servers behind DNAT? > > That's obviously a problem. But this problem is due to DNAT itself. > > If a mail server accepts any IP address, delivers locally for its own IP> address, and relays everything else, DNAT will still be a problem there. A mail > addressed to postmaster@[public ip address] which reach the server, which will> promptly attempt to relay it. Reverse lookup can be used to learn which domain's postmaster that would be,
That might be possible. The current implementation always uses the configured local domain (defaultdomain).
> I would also have to question whether anyone cares a lot about this legacy SMTP> feature. It is meant as a last resort, in case there's something wrong in the DNS. An extra bit of resiliency, which would almost never be used.
Well, what it's meant to be is one thing. What it actually is, is something that I would be surprised if it works correctly for more than one in a thousand domains, with the definition of "works" meaning that the mail gets delivered to someone who actually looks at it.
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