[LINK] RFC: emailing to <username>@<IP-Address>

[Roger Clarke]

Sorry, Link Institute, but I think we've been here before.

I just wrote to a bunch of MSc(ECommerce) candidates as follows.  If 
there's anything gravely wrong or misleading with what I said, please 
let me (and linkers) know.

Thanks!


Candidate asked:
>Q10. Can you email to someone at their IP-address rather than their 
>domain name?

Roger replied:

I said in a seminar that it is not possible to email to an IP-address.

I base this on:
(1)  my reading of RFC 2821, at http://www.ietf.org/rfc/rfc2821.txt
(2)  never having seen an email-address that includes an IP-address
(3)  experiments trying to send an email to the IP-address indicated in the
      MX-record for my own domain, i.e. Roger.Clarke at 203.20.62.11.
      This results in a 550 error from my IAP - 'recipient blocked'.

(I can't find a clear statement in the RFC that it isn't possible, 
but it's clear that the recipient is meant to be defined as a 
'mailbox' at a 'domain-name', and that the MX record in the 
authoritative domain-name server is intended to provide the 
translation from 'domain-name' to IP-address).


-- 
Roger Clarke                  http://www.anu.edu.au/people/Roger.Clarke/

Xamax Consultancy Pty Ltd      78 Sidaway St, Chapman ACT 2611 AUSTRALIA
                    Tel: +61 2 6288 1472, and 6288 6916
mailto:Roger.Clarke at xamax.com.au                http://www.xamax.com.au/

Visiting Professor in Info Science & Eng  Australian National University
Visiting Professor in the eCommerce Program      University of Hong Kong
Visiting Professor in the Cyberspace Law & Policy Centre      Uni of NSW