The DNSBL lbl.lagengymnastik.dk is no longer active. It ceased operation back in 2003 or 2004.
In January 2007, Henrik, the operator of this DNSBL, indicated that his bandwidth is still being greatly consumed by DNS queries against his blacklist. Because of this, he has implemented a “wildcard listing strategy” to force sites to stop using the list.
In a wildcard listing strategy, a DNSBL lists all IP addresses in the world. That means that anybody using this blacklist will no longer be able to receive any mail at all. This controversial “last resort” is done as a wake-up call for sites using the list. Suddenly they stop receiving all inbound mail, and hopefully they soon realize what’s going on and resolve it.
If you find your mail bouncing with a reference to the lbl.lagengymnastik.dk blacklist, contact the site that blocked your mail. I assume you’ll have to do that via telephone, since mail to them will not go through. Inform them that the blacklist is no longer around. Direct them to this site or recommend they do a Google search to learn more.