On Mon, Sep 05, 2005 at 05:43:41PM +0200, Julian Mehnle wrote:
If RFC 2821 doesn't modify the semantics of HELO as defined in RFC 821,
then are you saying that RFC 821 _already_ required the argument to HELO
to be a valid FQDN?
Apart from the exceptions (#123, [123.45.43.21]): Yes.
If that's what you're saying, then we'll have to agree to disagree,
because while RFC 821 may have some fuzzy and suggestive statements about
HELO, I just don't see it making any clear and strict requirements of
HELO.
Fuzzy and suggestive?
" HELO <SP> <domain> <CRLF>
"
So far, nothing fuzzy. Quite clear.
" The argument field contains the host name of the sender-SMTP
"
Dito.
" Domains are a recently introduced concept in the ARPA Internet
mail system. The use of domains changes the address space from a
flat global space of simple character string host names to a
hierarchically structured rooted tree of global addresses. The
host name is replaced by a domain and host designator which is a
sequence of domain element strings separated by periods with the
understanding that the domain elements are ordered from the most
specific to the most general.
For example, "USC-ISIF.ARPA", "Fred.Cambridge.UK", and
"PC7.LCS.MIT.ARPA" might be host-and-domain identifiers.
Whenever domain names are used in SMTP only the official names are
used, the use of nicknames or aliases is not allowed.
"
Still nothing else than a complete domain.
" Hosts are generally known by names which are translated to
addresses in each host. Note that the name elements of domains
are the official names -- no use of nicknames or aliases is
allowed.
"
And still nothing else than a domain. (exceptions follow below).
This is a well defined concept: the parameter needs to be (with
two mentioned exceptions) the official name, no aliases are allowed,
no nicknames, the sequence of domain elements ordered from the
most specific to the most general. It is quite clear to me that
this is an attempt to describe "FQDN" before it was invented.
Note: "names which are translated to addresses in each host." Can
you translate "jupiter" ? Probably not. If you can, insert something
else. You know what I mean.
It is "smtp.example.org", not "smtp", not "example.org", not "jupiter"
The (only) exceptions are: "#1234" and "[123.231.012.213]".
Those two exceptions caused havoc in the BNF. However, it is the
RFC that counts, not just the BNF. The RFC clearly states that
the exceptions are "#1234", not "#1234.example.org", and
"[123.231.12.213]", not "[123.231.12.213].[5.4.3.2].#1234".
(of course, these digits are an example from me, not from the rfc).
These exceptions are used only when necessary:
" Sometimes a host is not known to the translation function and
communication is blocked. To bypass this barrier two numeric
forms are also allowed for host "names".
"
Yes, "the translation function" is nowadays known as "DNS".
If this is not enough for you then yes, we have to agree not to agree.
Alex
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