In your previous mail you wrote: Hi, my PP mail MTA just received a message via x.400 originating in the x.400 ADMD Master400 in Italy. The sending user had requested a positive delivery report for the message. Unfortunately, my PP MTA was not configured to route the DR back via x.400, so it tried to use SMTP instead. Your system, corton.inria.fr is the preferred mail exchanger for the Master400.it domain and its subdomains. Sending back the DR via SMTP is not really a problem for my system (although it leads to loss of functionality of the sender of the original message), but unfortunately this failed. After looking into this a little further, it appears that it is corton.inria.fr which is the problem. My PP MTA said:

Your message was not delivered to VINCENZO.COZZOLINO@ENEL.ENELUTI.Master400.it for the following reason: Unknown Address MTA 'ENEL.ENELUTI.Master400.it' gives error message <VINCENZO.COZZOLINO@ENEL.ENELUTI.Master400.it>... hostname < ENEL . ENELUTI . Master400 . it > unknown to name-server

This was verified this way: % mconnect corton.inria.fr connecting to host corton.inria.fr (192.93.2.5), port 25 connection open 220 corton.inria.fr The EUnet gateway to France - Thu, 2 Jul 1992 13:44:06 + 0200 - (Sendmail+IDA+ 5.65c8d/92.02.29) vrfy vincenzo.cozzolino@enel.eneluti.master400.it 554 vincenzo.cozzolino@enel.eneluti.master400.it... hostname < enel . enelut i . master400 . it > unknown to name-server quit 221 corton.inria.fr closing connection % Which name-server is corton talking about? The master400.it domain has (as far as I can see) been properly registered in the DNS with both a "direct" MX and a wildcard MX for *.master400.it. The parties wanting to communicate would probably appreciate it if this problem could be fixed. If you could report back to me, I will notify the two parties wanting to communicate. Thanks. - Havard, (one of) postmaster@runit.sintef.no --> Havard, I (one of the manager of the EUnet-FR backbone machine: corton.inria.fr) would have been deeply flattered by Master400.it selecting us as their relay between SMTP and X.400 world (likely based on the excellence of our service). This choice would of course have led to some kind of 'contract', or at least minimum initial agreement; which we often accept in the context of EUnet to help connectivity. Unfortunatly, no such agreement exist, nor any initial agreement have ever been made between Master400 and EUnet-FR; agreement which would have allowed us to set up the proper dedicated routes directing to Master400 once the mail is caught by the MX on corton. You will certainly understand that it's quite hard for us to set up a special route (eg: non MX driven) for an entity we have never known of before. I suspect that this MX has been set by persons not understanding the full details and subtleties of MX, a well used tehcnique in the IP world. May I suggest those people read the excellent paper Piet Beertema once wrote in the context of RIPE DNS WG, as stored in ~ftp/ripe/doc/lpr/DNS-advice.txt on machine mcsun.eu.net Please note that this paper has been approved as a RIPE recommendation. It contains a good description of this "MX records surprise" (quoting Piet's paper): In a sense similar to point 3. Sometimes nameserver managers enter MX records in their zone files that point to external hosts, without first asking or even informing the systems managers of those external hosts. This has to be fought out between the nameserver manager and the systems managers involved. Only as a last resort, if really nothing helps to get the offending records removed, can the systems manager turn to the naming authority of the domain above the offending domain to get the problem sorted out. Here is what DNS query yield on corton:

Master400.it Server: corton.inria.fr Address: 192.93.2.5

Master400.it preference = 10, mail exchanger = corton.inria.fr Master400.it preference = 20, mail exchanger = infngw.infn.it Master400.it preference = 30, mail exchanger = cosine-gw.infn.it corton.inria.fr internet address = 192.93.2.5 infngw.infn.it internet address = 131.154.1.1 cosine-gw.infn.it internet address = 140.105.6.99 Another query for zone trasnfert for IT, as stored on NIS.GARR.IT shows the following setting up: master400 MX 10 corton.inria.fr master400 MX 20 infngw.infn.it master400 MX 30 cosine-gw.infn.it *.master400 MX 10 corton.inria.fr *.master400 MX 20 infngw.infn.it *.master400 MX 30 cosine-gw.infn.it And also: y-net MX 10 corton.inria.fr y-net MX 20 infngw.infn.it y-net MX 30 cosine-gw.infn.it *.y-net MX 10 corton.inria.fr *.y-net MX 20 infngw.infn.it *.y-net MX 30 cosine-gw.infn.it The latter one direct mail for *y-net.it to the gateway to ynet-gw, which happens to be chenas.inria.fr rather than corton.inria.fr The recommendation by YMU (Ynet management unit) are that an MX should point to chenas.inria.fr, and only to it. This later point has to be dealt with directly with Teleo in Bruxelles. Cordialement, Yves ---------------------------------------------------------------- Yves Devillers Internet: Yves.Devillers@inria.fr Institut National de Recherche Goodie-Oldie: ...!uunet!inria!devill en Informatique et Automatique Phone: +33 1 39 63 55 96 INRIA, Centre de Rocquencourt Fax: +33 1 39 63 53 30 BP 105, 78153 Le Chesnay CEDEX Twx: 633 097 F France.