🚀 go-pugleaf

In article <1993Jan10.162048.22777@blilly.uucp> bruce@blilly.uucp (Bruce Lilly) writes:
>I have found a few discrepancies between RFC821 and RFC822 regarding the
>contents of the Received header.
>
>1)	RFC821 section 4.1.1 requires the "from" and "by" clauses, while
>	RFC822 4.1 lists them as optional.

I don't believe this is a discrepancy.  RFC821 is only discussing the
new "Received:" header it adds, and is not referring to any pre-existing
header.

>2)	RFC821 prohibits unquoted special characters (including '<', '>',
>	and '@') in the optional "id" clause, while RFC822 requires that the
>	format of the msg-id used in that clause, if present, is
>		"<" local-part "@" domain ">".

The "id" clause is not the same as the msg-id.  That is, the msg-id, or
more fully, the "Message-ID:" header is a unique identifier of the
message.  The "id" clause in the "Received:" header could be just a
transaction ID with purely local meaning.  It might, for example, be an
identifier which can be used to locate log records retained on this
host.

>                                                              If the "by"
>clause is always provided, mail loops can be more quickly and more reliably
>detected by processing the information in the headers, but it is not
>acceptable for the machine to place any interpretation on comments.

If you really want to process the contents of "Received:" headers for
finding mail loops, what you need is the requirement that such headers
not be modified.  Then if there is a previous header from your own host,
there is a loop.  The exact syntax of headers generated by hosts other
than yours would seem to be of no importance.  I presume that your
sofware can be designed to recognize the "Received:" headers it has
generated.