Thanks for the answer, but I do not think this is an specific problem of the clam how-to or the cd-utils how-to. I also had these problems before. 
In the meantime I discovered that I cannot access FTP either. So if someone could just check my iptables? Perhaps the problem is in there....
Thanks
Chain INPUT (policy DROP)
target     prot opt source               destination
state_chk  all  --  anywhere             anywhere
local_chk  all  --  anywhere             anywhere
PPPconn    all  --  anywhere             anywhere
DROP       all  --  BASE-ADDRESS.MCAST.NET/4  anywhere
DROP       all  --  anywhere             BASE-ADDRESS.MCAST.NET/4
InboundICMP  icmp --  anywhere             anywhere
denylog    icmp --  anywhere             anywhere
InboundTCP  tcp  --  anywhere             anywhere           tcp flags:SYN,RST,ACK/SYN
denylog    tcp  --  anywhere             anywhere           tcp flags:SYN,RST,ACK/SYN
InboundUDP  udp  --  anywhere             anywhere
denylog    udp  --  anywhere             anywhere
gre-in     gre  --  anywhere             anywhere
denylog    gre  --  anywhere             anywhere
denylog    all  --  anywhere             anywhere
Chain FORWARD (policy DROP)
target     prot opt source               destination
state_chk  all  --  anywhere             anywhere
local_chk  all  --  anywhere             anywhere
ForwardedTCP  tcp  --  anywhere             anywhere           tcp flags:SYN,RST,ACK/SYN
ForwardedUDP  udp  --  anywhere             anywhere
denylog    all  --  anywhere             anywhere
Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination
PPPconn    all  --  anywhere             anywhere
DROP       all  --  BASE-ADDRESS.MCAST.NET/4  anywhere
DROP       all  --  anywhere             BASE-ADDRESS.MCAST.NET/4
OutboundICMP  icmp --  anywhere             anywhere
denylog    icmp --  anywhere             anywhere
ACCEPT     all  --  anywhere             anywhere
Chain ForwardedTCP (1 references)
target     prot opt source               destination
ForwardedTCP_6516  all  --  anywhere             anywhere
denylog    tcp  --  anywhere             anywhere           tcp flags:SYN,RST,ACK/SYN
Chain ForwardedTCP_6516 (1 references)
target     prot opt source               destination
Chain ForwardedUDP (1 references)
target     prot opt source               destination
ForwardedUDP_6516  all  --  anywhere             anywhere
denylog    udp  --  anywhere             anywhere
Chain ForwardedUDP_6516 (1 references)
target     prot opt source               destination
Chain InboundICMP (1 references)
target     prot opt source               destination
InboundICMP_6516  all  --  anywhere             anywhere
denylog    icmp --  anywhere             anywhere
Chain InboundICMP_6516 (1 references)
target     prot opt source               destination
denylog    icmp --  anywhere             anywhere           icmp echo-request
ACCEPT     icmp --  anywhere             anywhere           icmp echo-request
ACCEPT     icmp --  anywhere             anywhere           icmp echo-reply
ACCEPT     icmp --  anywhere             anywhere           icmp destination-unreachable
ACCEPT     icmp --  anywhere             anywhere           icmp source-quench
ACCEPT     icmp --  anywhere             anywhere           icmp time-exceeded
ACCEPT     icmp --  anywhere             anywhere           icmp parameter-problem
denylog    all  --  anywhere             anywhere
Chain InboundTCP (1 references)
target     prot opt source               destination
InboundTCP_6516  all  --  anywhere             anywhere
denylog    tcp  --  anywhere             anywhere           tcp flags:SYN,RST,ACK/SYN
Chain InboundTCP_6516 (1 references)
target     prot opt source               destination
denylog    all  --  anywhere            !pD9F9E190.dip0.t-ipconnect.de
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:auth
denylog    tcp  --  anywhere             anywhere           tcp dpt:ftp
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:www
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:https
denylog    tcp  --  anywhere             anywhere           tcp dpt:imap2
denylog    tcp  --  anywhere             anywhere           tcp dpt:ldap
denylog    tcp  --  anywhere             anywhere           tcp dpt:pop3
denylog    tcp  --  anywhere             anywhere           tcp dpt:1723
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:smtp
denylog    tcp  --  anywhere             anywhere           tcp dpt:ssh
denylog    tcp  --  anywhere             anywhere           tcp dpt:telnet
Chain InboundUDP (1 references)
target     prot opt source               destination
InboundUDP_6516  all  --  anywhere             anywhere
denylog    udp  --  anywhere             anywhere
Chain InboundUDP_6516 (1 references)
target     prot opt source               destination
denylog    all  --  anywhere            !pD9F9E190.dip0.t-ipconnect.de
Chain OutboundICMP (1 references)
target     prot opt source               destination
OutboundICMP_6516  all  --  anywhere             anywhere
denylog    icmp --  anywhere             anywhere
Chain OutboundICMP_6516 (1 references)
target     prot opt source               destination
ACCEPT     icmp --  anywhere             anywhere           icmp echo-request
ACCEPT     icmp --  anywhere             anywhere           icmp echo-reply
ACCEPT     icmp --  anywhere             anywhere           icmp destination-unreachable
ACCEPT     icmp --  anywhere             anywhere           icmp source-quench
ACCEPT     icmp --  anywhere             anywhere           icmp time-exceeded
ACCEPT     icmp --  anywhere             anywhere           icmp parameter-problem
denylog    all  --  anywhere             anywhere
Chain PPPconn (2 references)
target     prot opt source               destination
PPPconn_1  all  --  anywhere             anywhere
Chain PPPconn_1 (1 references)
target     prot opt source               destination
Chain denylog (27 references)
target     prot opt source               destination
DROP       udp  --  anywhere             anywhere           udp dpt:route
DROP       udp  --  anywhere             anywhere           udp dpts:netbios-ns:netbios-ssn
DROP       tcp  --  anywhere             anywhere           tcp dpts:netbios-ns:netbios-ssn
LOG        all  --  anywhere             anywhere           LOG level warning prefix denylog:'
DROP       all  --  anywhere             anywhere
Chain gre-in (1 references)
target     prot opt source               destination
denylog    all  --  anywhere            !pD9F9E190.dip0.t-ipconnect.de
denylog    all  --  anywhere             anywhere
Chain local_chk (2 references)
target     prot opt source               destination
local_chk_6516  all  --  anywhere             anywhere
Chain local_chk_6516 (1 references)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere
ACCEPT     all  --  192.168.7.0/24       anywhere
Chain state_chk (2 references)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere           state RELATED,ESTABLISHED