2.67 and 2.68 kernels

[esarakaitis]

net.ipv4.tcp_default_win_scale=0
net.ipv4.tcp_moderate_rcvbuf=0


these two lines need to be in /etc/sysctl.conf for smtp to function correctly

[esarakaitis]

sticky this please...


Kernels 2.6.7 and 2.6.8 come with changes to the tcp window size that (should) increase the efficiency of tcp. What it HAS done is expose a problem with the way some routers and firewalls handle requests for large windows. Those routers and firewalls just refuse to handle them; which is why you may be able to access some sites, but not others.

The quick fix is to su to root and do two things:

#echo "net.ipv4.tcp_moderate_rcvbuf=0" >> /etc/sysctl.conf
#echo "net.ipv4.tcp_default_win_scale=0" >> /etc/sysctl.conf

..and then reboot. Alternately, you can just issue:

#/sbin/sysctl -w net.ipv4.tcp_moderate_rcvbuf=0
#/sbin/sysctl -w net.ipv4.tcp_default_win_scale=0

...and save yourself the reboot, but your settings will be lost when you DO reboo