On 2022-08-11 at 07:56:41 UTC-0400 (Thu, 11 Aug 2022 12:56:41 +0100)
Nick Howitt <n...@howitts.co.uk>
is rumored to have said:
I can't use reject_unknown_client_hostname as I know at least one
major ISP in the UK has their mailserver announcing a ???.local or
???.lan domain.
1. Ewww. That's so '90s.
2. The HELO name is not relevant to reject_unknown_client_hostname.
There is a reject_unknown_helo_hostname restriction, but I suspect it
only exists for logical completeness, as using it would be infeasible on
any machine acting as a MX.
Also don't the RFC's require an FQDN as a hostname but it does not
necessarily need to be valid? Or am I thinking of something else?
The phrase "RFC's require" is fraught with potential for
misinterpretation.
The HELO/EHLO name SHOULD be a FQDN, it SHOULD be resolvable by any
machine that sees it via an A or AAAA record, and it SHOULD resolve back
top the connecting IP address. RFC821 and its successors have all said
something like that but they have also all said you MUST NOT reject
messages solely because the HELO name is wrong.
--
Bill Cole
b...@scconsult.com or billc...@apache.org
(AKA @grumpybozo and many *@billmail.scconsult.com addresses)
Not Currently Available For Hire
