🚀 go-pugleaf

Excerpts from: 11-Apr-88 Re: Are underbars considere.. Per Hedeland@erix.UUCP
(735)
> Where does this notion that periods are not allowed in unquoted local-parts
> come from (I've encountered it in other places as well)? As far as I can
> understand, RFC822 quite to the contrary explicitly allows this...

First of all, Ron Natalie's message said that periods were illegal in
``atom''s, not in ``local-part''s.  He is correct, as are you, but he was
talking about an RFC822 atom, and you're talking about an RFC822 local-part.

One can also confuse ``phrase'' with ``local-part''.  For obscure (perhaps
mistaken) reasons, RFC822 allows (unquoted) periods in local-parts but not in
phrases, and allows (unquoted) spaces in phrases but not in local parts.
``phrase'' is what's to the left of an angle-bracket address in a header;
local-part is what's immediately to the left of an at-sign.  Thus,
        To: Craig Everhart <Craig.Everhart@andrew.cmu.edu>
is a legal header on both counts, but
        To: Craig F. Everhart <Craig Everhart@andrew.cmu.edu>
is illegal on both.

There were a lot of inertia-based reasons for disallowing spaces in a
local-part.  Disallowing periods in a phrase is probably an oversight, but
we're stuck with it.  Another curiosity is that a phrase can't be null in a
message header, so the header
        To: <Craig.Everhart@andrew.cmu.edu>
is, strictly speaking, illegal.  (When we have to use a return-path (which, if
it's a source-route, can require the ``<'' and ``>'' characters) to compose an
error message, sometimes we have to generate a non-null phrase to precede them.
 I used to use the text constant ``dummy'', representing a syntactic dummy, but
when people started to take it as a mild insult, I had to change it to
``Message sender''!)

                Craig Everhart
                Andrew message system