I've just sent the below email to Hetzner.de support:
I'm one of the administrators of the hetzner.de server used to host numerous services supporting the squeak.org project. Our server is 85.10.195.197. Lately we've been having trouble sending email to some users and it appears that the problem is with the DNS servers we are using, checking the wiki these still seem to be the preferred servers (http://wiki.hetzner.de/index.php/Hetzner_Standard_Name_Server/en):
$ cat /etc/resolv.conf nameserver 213.133.98.98 nameserver 213.133.99.99 nameserver 213.133.100.100
As a test I try my own domain name:
$ dig @213.133.99.99 kencausey.com mx
; <<>> DiG 9.2.4 <<>> @213.133.99.99 kencausey.com mx ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 48963 ;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 2, ADDITIONAL: 0
;; QUESTION SECTION: ;kencausey.com. IN MX
;; ANSWER SECTION: kencausey.com. 3600 IN MX 0 smtp.secureserver.net. kencausey.com. 3600 IN MX 10 mailstore1.secureserver.net.
;; AUTHORITY SECTION: kencausey.com. 3600 IN NS ns42.domaincontrol.com. kencausey.com. 3600 IN NS ns41.domaincontrol.com.
;; Query time: 330 msec ;; SERVER: 213.133.99.99#53(213.133.99.99) ;; WHEN: Sat Nov 9 18:42:46 2013 ;; MSG SIZE rcvd: 147
It works fine. Yet for two other domain names we know of it does not work:
$ dig @213.133.99.99 mindspring.com mx
; <<>> DiG 9.2.4 <<>> @213.133.99.99 mindspring.com mx ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 25532 ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION: ;mindspring.com. IN MX
;; Query time: 3 msec ;; SERVER: 213.133.99.99#53(213.133.99.99) ;; WHEN: Sat Nov 9 18:43:32 2013 ;; MSG SIZE rcvd: 32
$ dig @213.133.100.100 mypacks.net mx
; <<>> DiG 9.2.4 <<>> @213.133.100.100 mypacks.net mx ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 52906 ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION: ;mypacks.net. IN MX
;; Query time: 3 msec ;; SERVER: 213.133.100.100#53(213.133.100.100) ;; WHEN: Sat Nov 9 18:44:53 2013 ;; MSG SIZE rcvd: 29
And yet it works elsewhere:
$ dig @8.8.8.8 mypacks.net mx
; <<>> DiG 9.2.4 <<>> @8.8.8.8 mypacks.net mx ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2192 ;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION: ;mypacks.net. IN MX
;; ANSWER SECTION: mypacks.net. 2 IN MX 5 mx3.earthlink.net. mypacks.net. 2 IN MX 5 mx4.earthlink.net. mypacks.net. 2 IN MX 5 mx1.earthlink.net. mypacks.net. 2 IN MX 5 mx2.earthlink.net.
;; Query time: 5 msec ;; SERVER: 8.8.8.8#53(8.8.8.8) ;; WHEN: Sat Nov 9 18:45:32 2013 ;; MSG SIZE rcvd: 119
$ dig @8.8.8.8 mindspring.com mx
; <<>> DiG 9.2.4 <<>> @8.8.8.8 mindspring.com mx ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 53905 ;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION: ;mindspring.com. IN MX
;; ANSWER SECTION: mindspring.com. 13 IN MX 5 mx4.mindspring.com. mindspring.com. 13 IN MX 5 mx1.mindspring.com. mindspring.com. 13 IN MX 5 mx2.mindspring.com. mindspring.com. 13 IN MX 5 mx3.mindspring.com.
;; Query time: 6 msec ;; SERVER: 8.8.8.8#53(8.8.8.8) ;; WHEN: Sat Nov 9 18:46:02 2013 ;; MSG SIZE rcvd: 112
Please advise us if we should be using alternate DNS servers.