DNS-problem with Speedtouch 510

[Maja]

Hello,

I have registered a domain name and I´m trying to configure a
DNS-server. The DNS-server is working just fine locally, I´ve tested
it with the dig command in Linux. Port 53 is opened in the firewall,
both UDP and TCP.

I´m unable to use the dig command from a computer outside my network
(from internet). I get the following message:

dig @xx.xxx.xxx.xxx domainname.com

; <<>> DiG 9.2.1 <<>> @xx.xxx.xxx.xxx domainname.com
;; global options:  printcmd
;; connection timed out; no servers could be reached

I tried to turn off the firewall in Speedtouch 510 but it makes no
difference.
When I try to connect to the DNS-server using Telnet I get the
following message:

telnet xx.xxx.xx.xxx 53
Trying xx.xxx.xx.xxx...
Connected to xx.xxx.xx.xxx.


What can be wrong??? Please help me, I have tried everything!!

/Maja