Xref: utzoo comp.mail.headers:654 comp.mail.misc:5017 Path: utzoo!news-server.csri.toronto.edu!rutgers!usc!zaphod.mps.ohio-state.edu!mstar!mstar.morningstar.com!bob From: bob@MorningStar.Com (Bob Sutterfield) Newsgroups: comp.mail.headers,comp.mail.misc Subject: Unreplyable addresses not considered illegal enough? Message-ID: Date: 10 Mar 91 21:33:42 GMT Sender: usenet@MorningStar.COM (USENET Administrator) Followup-To: comp.mail.headers Organization: Morning Star Technologies Lines: 26 By an unreplyable address, I mean an address to which mail cannot be sent, but which is found in the From: or Reply-To: header line of a mail or news message. Common and obvious examples are simply malformed non-addresses (e.g. joe@undotted-name or site!joe or joe%site); but more subtle ones include well-formed addresses that are continually inaccessible, such as those for which valid MX records are available but which direct the SMTP socket toward an un"connected" network (e.g. pentagon-ai.army.mil). The only explicit reference I can find to unreplyable From: lines is in RFC1123, section 5.3.7(D) of the discussion of gatewaying between the Internet and other mail systems, where we find that `... all addresses ... must be effective and useful for sending replies.' (Note that 5.3.7 discusses mail that crosses mail network boundaries, but not Internet-only mail!) This is at least a bit more explicit than RFC822, section 4.4.1 of the discussion of the From: field, where we see that `... addresses in the "From" field must be machine-usable (addr-specs) ...' One might broadly interpret "machine-usable" to mean "accessible via SMTP and the DNS", but that seems to be stretching the interpretation a bit further than most Talmudic scholars of the RFCs would prefer. I think that most mail users and administrators would agree that unreplyable From: or Reply-To: lines are Wrong. Why is there no stronger and more specific prohibition?