On Dec 22, 2019, at 5:44 AM, Alessandro Vesely <vesely(_at_)tana(_dot_)it>
wrote:
On Dec 21, 2019, at 3:47 PM, Keith Moore wrote:
DNS is nowhere nearly universal, and cannot be.
There is deliberately no name resolution dependency (DNS or
otherwise) in the code that determines the system hostname.
I guess recipient email addresses have to be given in dotted quad too...?
No, that conclusion does not follow. While the system hostname is
determined "statically", with no name service lookups, the nexthop
domain is subject to name resolution, which defaults to "dns", but
can be set to "dns, native" on mixed networks, or just "native" on
networks where DNS is not available.
Of course if one wants to send mail to "luser@[192.0.2.1]" that'll
work too (but that address form isn't by default accepted via SMTP
from clients that are neither on a local network nor by some means
authenticated, an open-relay configuration als possible, though it
is not likely to be enabled just by accident.
--
Viktor.
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