Your mail server does not have reverse DNS set up properly:

2003-05-27 12:32:41 recipient
<php-blog-devs-request@lists.sourceforge.net> refused from (yourmail.dk) [195.184.125.21]
sender=<webmaster@tsn.dk> (failed to find host name from IP address)


sc8-sf-list1:~# host yourmail.dk
yourmail.dk             A       195.184.125.23
sc8-sf-list1:~# host 195.184.125.21
195.184.125.21 does not exist, try again
sc8-sf-list1:~# host 195.184.125.23
195.184.125.23 does not exist, try again
sc8-sf-list1:~#