[rfc-i] Erratum: RfC 2822 section 3.2.6 <unstructured> ABNF

Frank Ellermann nobody at xyzzy.claranet.de
Tue Jan 10 00:42:20 PST 2006

Hi, RFC 2822 section 3.2.3 states:

   There are several places in this standard where comments and FWS may
   be freely inserted.  To accommodate that syntax, an additional token
   for "CFWS" is defined for places where comments and/or FWS can occur.
   However, where CFWS occurs in this standard, it MUST NOT be inserted
   in such a way that any line of a folded header field is made up
   entirely of WSP characters and nothing else.

In section 3.2.6 it defines <unstructured> header field bodies:

   unstructured    =       *([FWS] utext) [FWS]

A prominent example is the <subject> defined in section 3.6.5:

   subject         =       "Subject:" unstructured CRLF

Expanding the [FWS] at the end (ignoring <obs-FWS>) results in:

   subject = "Subject:" *([FWS] utext) [[*WSP CRLF] 1*WSP] CRLF

This is not intended and forbidden by a MUST NOT in 3.2.3, the
ABNF for <unstructured> in section 3.2.6 shoukd have this form:

   unstructured    =       *([FWS] utext) (*WSP / obs-FWS)

                      Kind regards, F.Ellermann

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