Path: utzoo!attcan!uunet!mailrus!cornell!parmelee From: parmelee@wayback.cs.cornell.edu (Larry Parmelee) Newsgroups: comp.mail.uucp Subject: Re: Paths and Precedence (Re: Question about From: lines) Message-ID: <42765@cornell.UUCP> Date: 28 Jun 90 16:42:37 GMT References: <2833.2674c5b3@mccall.com> <14298@ucsd.Edu> <2836.26750678@mccall.com> <14423@ucsd.Edu> <00001FL@cdis-1.compu.com> <2999.2688d45c@mccall.com> Sender: nobody@cornell.UUCP Reply-To: parmelee@wayback.cs.cornell.edu (Larry Parmelee) Organization: Cornell Univ. CS Dept, Ithaca NY Lines: 27 In article peter@ficc.ferranti.com (Peter da Silva) writes: > ... What's the official word on % versus !? See RFC 1123 "Requirements for Internet hosts - application and support", section 5.2.16, "RFC-822 Local-part: RFC-822 Section 6.2". Quoting from second from last paragraph in that section, ... This is commonly known as the "%-hack". It is suggested that "%" have lower precedence than any other routing operator (e.g., "!") hidden in the local-part; for example, "a!b%c" would be interpreted as "(a!b)%c". Using parens to indicate precidence in mail addresses may be misleading- it may be clearer to say that "a!b%c" should be parsed as "HOST ! MAILBOX", where "HOST" is "a" and "MAILBOX" is "b%c". The message should be sent to HOST, and then it's up to HOST to interpret the MAILBOX part. The above quote (and a little bit of surrounding context in the RFC) is the ONLY official definition of "the %-hack" that I'm aware of, and a weak definition it is, too, since they only said "suggested". In parsing a mail address, I ignore "%"s if there's any other routing characters available, and I avoid using "%"s in any addresses I generate. -Larry Parmelee parmelee@cs.cornell.edu