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TLDs with MXs

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29th Mar 2007 | 14:32

There's currently a discussion on the IETF SMTP mailing list about the exact syntax of the domain part of an email address, since the cleaned-up ABNF in RFC 2821 unintentionally forbade domains with a single label. The argument is how to fix this error, whether the discrepancy between DNS syntax (optional trailing dot for FQDNs) and SMTP syntax (no trailing dot ever) matters, and whether email to a bare top-level domain makes any sense.

Arnt Gulbrandsen noticed that a surprisingly large number of TLDs have MX records, so I thought it might be interesting to list all 26 of them...

$ dig axfr . @f.root-servers.net. |
  sed 's/^V^I/ /g;/\..* NS .*/!d;s///' |
  uniq | tr A-Z a-z |
  while read d; do
    dig mx $d. |
    sed 's/^V^I/ /g;/\..* MX /!d;s//. MX /' |
    grep . && whois -h whois.iana.org $d |
    sed '/Country:/!d;s///' | uniq;
  done |

ac. A                              ; not listening
     Ascension Islands
ai. MX 10 mail.offshore.ai.        ; seems to work <vince@ai> (sendmail/ubuntu "No UCE/UBE")
as. MX 10 dca.relay.gdns.net.      ; accepts anything (sendmail)
as. MX 20 jfk.relay.gdns.net.      ; accepts anything (sendmail)
as. MX 30 lhr.relay.gdns.net.      ; accepts anything (sendmail)
     American Samoa
bi. A                              ; not listening
bj. MX 10 bow.intnet.bj.           ; accepts anything (postfix)
bj. MX 20 bow.rain.fr.             ; not listening
cf. MX 10 bow.intnet.cf.           ; relaying denied (sendmail)
     Central African Republic
cm. A                              ; not listening
cx. MX 5 mail.nic.cx.              ; relaying denied (exim/@mail)
     Christmas Island
dj. MX 5 smtp.intnet.dj.           ; relaying denied (trend anti-virus)
dj. MX 10 bow.intnet.dj.           ; not listening
dj. MX 20 bow.rain.fr.             ; not listening
dk. A                              ; rejects everything (postfix)
dm. MX 10 mail.nic.dm.             ; relaying denied (imail)
gp. MX 5 ns1.nic.gp.               ; relaying denied (sendmail "I enjoy loveletters")
gp. MX 10 ns34259.ovh.net.         ; relaying denied (qmail)
gp. MX 20 manta.outremer.com.      ; not listening
gt. MX 10 mail.gt.                 ; not listening
hr. MX 10 alpha.carnet.hr.         ; accepts anything (exim/debian)
im. MX 10 mail.advsys.co.uk.       ; relaying denied (msexchange)
im. A                              ; ignored
     Isle of Man
io. MX 10 mailer2.io.              ; seems to work <paul@io> (sendmail)
io. A                              ; ignored
     British Indian Ocean Territory
kh. MX 10 ns1.dns.net.kh.          ; not listening
km. MX 100 mail1.comorestelecom.km.; relaying denied (sendmail)
km. MX 110 bow.snpt.km.            ; no such host
     Comoros                       ; SOA contains <root@km>
mh. MX 10 imap.pwke.twtelecom.net. ; accepts anything (?)
mh. MX 20 mx1.mail.twtelecom.net.  ; relay denied (postfix)
mh. MX 30 mx2.mail.twtelecom.net.  ; relay denied (postfix)
     Marshall Islands
mq. MX 10 mx.mediaserv.net.        ; domain not fully-qualified (postfix/debian)
ne. MX 10 bow.intnet.ne.           ; relaying denied ("*****")
ne. MX 20 bow.rain.fr.             ; not listening
ni. MX 0 ns2.ni.                   ; relaying denied (sendmail)
ni. MX 10 ns.ni.                   ; not listening
pa. MX 5 ns.pa.                    ; relaying denied
ph. A                              ; not listening
pn. A                              ; rejects everything (exim)
pw. A                              ; relaying denied (sendmail)
sh. A                              ; not listening
     St Helena
td. MX 10 mail.intnet.td.          ; relaying denied (sendmail)
td. MX 20 bow.rain.fr.             ; not listening
tk. MX 100 ATAFU.TALOHA.tk.        ; seems to work <joost@tk> (postfix)
tl. MX 5 mail.nic.tl.              ; relaying denied (exim/@mail)
tm. A                              ; not listening
tt. MX 0 66-27-54-138.san.rr.com.  ; seems to work <admin@tt> (sendmail)
tt. MX 10 66-27-54-142.san.rr.com. ; relaying denied (postfix/ubuntu)
     Trinidad and Tobago
ua. MX 5 km.nic.net.ua.            ; seems to work <hostmaster@ua> (sendmail)
ua. MX 20 mx1.he.kolo.net.         ; seems to work (sendmail)
uz. A                              ; not listening
va. MX 10 lists.vatican.va.        ; accepts anything (postfix)
va. MX 20 paul.vatican.va.         ; not listening
va. MX 50 proxy2.urbe.it.          ; relaying denied (qmail)
va. MX 90 john.vatican.va.         ; not listening
ws. MX 10 mail.worldsite.ws.       ; relaying denied ("*****")
ws. A                              ; ignored

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Comments {6}

from: dwmalone
date: 29th Mar 2007 15:47 (UTC)

ie used to have them too I believe, though that was fixed by a mutual friend of ours.

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(Deleted comment)

Tony Finch

from: fanf
date: 29th Mar 2007 16:18 (UTC)

It comes with everything. In fact, it's the only software most people know how to use...

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from: arnhem
date: 29th Mar 2007 16:13 (UTC)

Reminds me of the little bug I found in IE (five or so years ago) - it assumed that any single-component hostname in a url _must_ be in the local security zone, but resolved single-component hostnames that corresponded to tlds with A records as the tld .

As far as I can tell, MS ignored the bug report made via a colleague, so it might still exist.

At the time, I did the same kind of trawl; there were a surprising number of web servers lurking on tlds ...

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Tony Finch

from: fanf
date: 29th Mar 2007 16:23 (UTC)

Speaking of ie (the one you refer to AND the one dwmalone refers to), there was an amusing incident at Demon when IE3 was released. Microsoft made it available as a free download, and Demon hosted one of the download sites on its Homepages service, under the name ie.demon.co.uk - the first two-letter name in that zone. This caused all sorts of breakage with communication with Ireland because of the usual search path in use in Demon at the time. (Sadly history does not relate the details of the breakage.)

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from: anonymous
date: 3rd Apr 2007 08:05 (UTC)

I wonder how many of these domains actually sell email services. I wonder whether these are taken: "pope@va" "knights@ni" "en0@io" "lt@gt" "rap@dj" "robot@ai" "rasm@as"?

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Tony Finch

Re: pope@va

from: fanf
date: 3rd Apr 2007 08:48 (UTC)

Non-intrusive testing means I can't be sure what an MTA does with messages it accepts, but given that caveat...

va is horribly misconfigured - most of the MXs don't recognise the domain, and the primary MX accepts any local part.

So is ni - one MX doesn't recognise the domain and the other isn't running an SMTP server. (And the MX points to two of the primary nameservers?!)

io seems to be run competently - postmaster@io is accepted, rnadomstuff@io is not. Sadly eno@io is not either. A look at http://www.nic.io/about.html suggests something else to test and paul@io does indeed work.

I can't connect to any of the gt MXs.

dj is also broken.

ai is similar to io in that it's run like a vanity domain with attached registry - www.ai hints that vince@ai works and not much else.

as accepts anything.

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