spf-discuss
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[spf-discuss] Re: Inconsistency in SPF spec re. "domain-spec"

2006-03-23 01:18:17
william(at)elan.net wrote:

domain-spec      = macro-string domain-end
domain-end       = ( "." toplabel ) / macro-expand
toplabel         = ALPHA / ALPHA *[ alphanum / "-" ] alphanum
                    ; LDH rule (See [RFC3696])

Nothing's wrong here, only "must start with ALPHA" is a bit
_too_ restrictive wrt 3696:  The 3696 toplabel rule is "must
contain not only digits".  But so far that exists only in a
USEFOR draft as ABNF, 3696 hat it in prose.

The SPF spec. took the simple toplabel ABNF of 2396 (obsolete).
The "official" toplabel rule is even more restrictive than SPF.

No issue here from our POV, and we don't need any trailing dot.

underscores are not a problem because allocated domain
(toplabel) should not have any underscores

ACK.  And SPF like DNS intentionally allows for labels that are
not valid in a host name.  From a DNS POV any octet is allowed.

SPF restricts that to VCHAR (printable ASCII) plus space minus
dot.  Of course you'd need a macro for space.  We draw the line
at CTL, SP, and 8bit-octets, nobody needs this for SPF, they're
all not allowed in LDH host names.

                            Bye, Frank


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