Problem with sendmail 8.13.7

[Alexander Dalloz]

Stefan Kuhlemann schrieb:

> even more strange - today around 10:00 o'clock the sendmail started to 
> work normal until 16:00 o'clock. (with nothing changed since sunday 
> 22:00)
>
> My feelings tell me that the reason might be some strange 'ill-broken' 
> firewall network stack or some weird netwok communication issues (like 
> the 'fun' with the ECN-flag some years ago)
> I'm tomorrow 'on-site'......
>
> Stefan

Try following kernel parameter change

sysctl -w net.ipv4.tcp_window_scaling=0

and see if that helps. TCP window scaling behaviour changed with kernel 
2.6.17 to be again more aggressive[1]. Some other systems are just 
broken in this regard.

Alexander