Now it works for me! I made the registry entry with MTU=1300 and I receive postbank.de and wallstreet-journal.de. genie.de does not work yet...
The speedGuide analysis is:
TCP options string = 020405ac01010402
MTU = 1492
MTU is optimized for PPoE DSL broadband. If not, consider raising MTU to 1500 for optimal throughput.
MSS = 1452
MSS is optimized for PPPoE DSL broadband. If not, consider raising your MTU value.
Default TCP Receive Window (RWIN) = 65340
RWIN Scaling (RFC1323) = 0 bits
Unscaled TCP Receive Window = 65340
RWIN is a multiple of MSS
Other RWIN values that might work well with your current MTU/MSS:
511104 (MSS x 44 * scale factor of 8)
255552 (MSS x 44 * scale factor of 4)
127776 (MSS x 44 * scale factor of 2)
63888 (MSS x 44)
bandwidth * delay product (Note this is not a speed test):
Your TCP Window limits you to: 2613.6 kbps (326.7 KBytes/s) @ 200ms
Your TCP Window limits you to: 1045.44 kbps (130.68 KBytes/s) @ 500ms
MTU Discovery (RFC1191) = ON
Time to live left = 119 hops
TTL value is ok.
Timestamps (RFC1323) = OFF
Selective Acknowledgements (RFC2018) = ON
IP type of service field (RFC1349) = 00000000 (0)