name resolution problem: daadjp.com (bind 8.1)

[Bernd Plagge]

Hello,

one of our customers (domain: daadjp.com) has problems to receive mail
from its headoffice (daad.de) the reason being that headoffice
nameserver (merlin.daad.de) doesn't respond / times out.
BTW, the timeout seems to be set to 2 secs.

fpdns merlin.daad.de tells me that they are running Bind 8.1 - 8.2.1-T4B
(recurson enabled)

dig @merlin.daad.de mx daadjp.com 

results in:
; <<>> DiG 9.3.1 <<>> @merlin.daad.de mx daadjp.com
; (1 server found)
;; global options:  printcmd
;; connection timed out; no servers could be reached

while
dig @merlin.daad.de mx daadjp.com +trace
results in:
; <<>> DiG 9.3.1 <<>> @merlin.daad.de mx daadjp.com +trace
; (1 server found)
;; global options:  printcmd
.                       67830   IN      NS      I.ROOT-SERVERS.NET.
.                       67830   IN      NS      J.ROOT-SERVERS.NET.
.                       67830   IN      NS      K.ROOT-SERVERS.NET.
.                       67830   IN      NS      L.ROOT-SERVERS.NET.
.                       67830   IN      NS      M.ROOT-SERVERS.NET.
.                       67830   IN      NS      A.ROOT-SERVERS.NET.
.                       67830   IN      NS      B.ROOT-SERVERS.NET.
.                       67830   IN      NS      C.ROOT-SERVERS.NET.
.                       67830   IN      NS      D.ROOT-SERVERS.NET.
.                       67830   IN      NS      E.ROOT-SERVERS.NET.
.                       67830   IN      NS      F.ROOT-SERVERS.NET.
.                       67830   IN      NS      G.ROOT-SERVERS.NET.
.                       67830   IN      NS      H.ROOT-SERVERS.NET.
;; Received 436 bytes from 194.94.212.2#53(194.94.212.2) in 341 ms

com.                    172800  IN      NS      H.GTLD-SERVERS.NET.
com.                    172800  IN      NS      I.GTLD-SERVERS.NET.
com.                    172800  IN      NS      J.GTLD-SERVERS.NET.
com.                    172800  IN      NS      K.GTLD-SERVERS.NET.
com.                    172800  IN      NS      L.GTLD-SERVERS.NET.
com.                    172800  IN      NS      M.GTLD-SERVERS.NET.
com.                    172800  IN      NS      A.GTLD-SERVERS.NET.
com.                    172800  IN      NS      B.GTLD-SERVERS.NET.
com.                    172800  IN      NS      C.GTLD-SERVERS.NET.
com.                    172800  IN      NS      D.GTLD-SERVERS.NET.
com.                    172800  IN      NS      E.GTLD-SERVERS.NET.
com.                    172800  IN      NS      F.GTLD-SERVERS.NET.
com.                    172800  IN      NS      G.GTLD-SERVERS.NET.
;; Received 500 bytes from 192.36.148.17#53(I.ROOT-SERVERS.NET) in 169
ms

daadjp.com.             172800  IN      NS      ns.choicenet.ne.jp.
daadjp.com.             172800  IN      NS      ns02.choicenet.ne.jp.
;; Received 79 bytes from 192.43.172.30#53(I.GTLD-SERVERS.NET) in 319 ms

daadjp.com.             86400   IN      MX      10 mail.daadjp.com.
daadjp.com.             86400   IN      MX      20 mail02.daadjp.com.
daadjp.com.             259200  IN      NS      ns.choicenet.ne.jp.
daadjp.com.             259200  IN      NS      ns02.choicenet.ne.jp.
;; Received 123 bytes from 203.141.151.81#53(ns.choicenet.ne.jp) in 5 ms

The total time required for the lookup is less than 2 secs but it seems
that sometimes the limit is exceeded.
Even without dig it says: 1 server found
but then nothing follows.

Any idea what the problem might be?

Thanks

Bernard