Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!mailrus!tut.cis.ohio-state.edu!bloom-beacon!mit-eddie!bbn!rochester!pt.cs.cmu.edu!andrew.cmu.edu!cfe+ From: cfe+@andrew.cmu.edu (Craig F. Everhart) Newsgroups: comp.mail.headers Subject: Re: Are underbars considered bad form for addresses in RFC822 headers? Message-ID: Date: 14 Apr 88 15:08:21 GMT References: <4289@hoptoad.uucp> , <1600@erix.UUCP> Organization: Carnegie Mellon University Lines: 33 In-Reply-To: <1600@erix.UUCP> 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 is a legal header on both counts, but To: Craig F. Everhart 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: 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