Viktor Dukhovni: > That said, clearly some packets from the sender are lost, and never > retransmitted. The TCP connection negotiates selective ACK and > window scaling on both sides. First thing I would do is disable > window scaling on your Postfix server. This will reduce throughput > for mail from far away senders (without window scaling Hong Kong > to USA will be at most 64KB per ~0.25 sec or 4 sec per MB of data).
Postfix 2.6 and later have a workaround for TCP window scaling bugs. For detailed instructions, see: http://www.postfix.org/postconf.5.html#tcp_windowsize Wietse
