List Mail User a écrit :
[snip]
Leave the FQDN part out and you can try to base an argument on 2821,
but there sections 2.3.4 and 2.3.5 simply and clearly states that "Domain
names are used as names of hosts and of other entities in the domain name
hierarchy." So there seems little left to argue about and "single dot rule",
even a "no dot" case is allowed in RFC2821 - "consists of one or more", though
I don't believe any such hosts still exist.
agreed.
"localhost" is an fqdn with no dots. (also in theory, some TLDs have
A/MX records, so they could send mail and thus helo as their tld name.
but fortunately, these don't send mail, so they can be ignored).
also, the "matching" argument seems to be misinterpreted. the
requirement (in my understanding) is that
ip(helo) = client_ip
not helo = rdns or mx(helo) = foo_bar
