🚀 go-pugleaf

In article <1992Nov5.024040.13063@kirk.bu.oz.au>, bambi@bu.oz.au (David J. Hughes) writes:
|> C.V.Copas@lut.ac.uk writes:
|> 
|> >Well it doesn't SEEM to be a FAQ, so here goes. I wish to get mail to an
|> >Australian machine
|> >which I can verify is on the Internet by using <nslookup>. However, all my mail
|> >vanishes into oblivion without any feedback to myself. Nor am I able to <ping>
|> >the machine. Therefore, I have reasoned that I need to supply a routing node
|> >specification, yes? Question: do any tools exist for determining that node? 
|> 
|> 
|> You can use nslookup to find the MX relay host for your target.  Many
|> hosts down here are in the DNS but don't actually connect to the net
|> (ie. similar to usage of UUCP in the State etc.).
|> 
|> If you can't get it through the MX gateway, you can always drop the
|> postmaster on that host a line to find out why.

I mailed Conn about this and it transpires that he and I can telnet to port 25 on
the machine but not ping it. There is no MX for the host concerned but there
is an MX for dsto.gov.au which points to fang.dsto.gov.au first and then to
yoyo.aarnet.edu.au

e.g.

$ telnet csd0.dsto.gov.au 25
Trying 131.185.10.4...
Connected to csd0.dsto.gov.au.
Escape character is '^]'.
220 CSD0.DSTO.GOV.AU TGV/MultiNet SMTP service ready.
helo bats.comp.vuw.ac.nz
250 CSD0.DSTO.GOV.AU ; Hello bats.comp.vuw.ac.nz, pleased to meet you.
vrfy postmaster 
250 CSD Postmaster <postmaster>
quit
221 CSD0.DSTO.GOV.AU TGV/MultiNet SMTP service complete.
Connection closed by foreign host.

But if you 'ping' it you get:

$ ping csd0.dsto.gov.au.
ICMP Host Unreachable from gateway dsto.gw.au (139.130.176.2)
 for icmp from bats.comp.vuw.ac.nz (130.195.8.13) to csd0.dsto.gov.au (131.185.10.4)

I suspect it's some sort of security measure in the router but it's a little
strange.