How to tune TCP for heavily loaded sendmail box

[Andrew Chan]

Greetings,

I am running a relaying sendmail box and I would like it to be able to
handle up to 600 or so concurrent (incoming or outgoing) connections.

I tried that and discovered that TONS of incoming connections are stuck at
SYNC_RECV state. It is like the sendmail box received these port 25
connection attempts and then didn't know what to do with them.

I suspect I need to tune some of the TCP parameters so that the system can
handle many short lived TCP connections in an efficent manner. Any pointer
to this specific issue or general TCP tunning under Linux (2.4.2-ac28
kernel) will be most appreciated.

Thanks.

Andrew