Rolf E. Sonneveld: > In general, Postfix is running fine and this Postfix instance is also > running fine. However, there is one SMTP client (of which we are not in > control), that sends messages with long lines to this server running > Postfix. There is a problem with the communication between this client > and the server: whenever the clients sends a message which includes one > long line (377 characters, excluding the CRLF), the client seems to > 'hang' after character # 256 of this long line is transmitted. Then, > after some time the connection times out.
A tcpdump recording will reveal if the client stops sending or if the server stops reading (it's revealed by TCP receive window size). Once this is known the search can be focused. It could be somethinh as stupid as poorly-implemented anti-virus software. http://www.postfix.org/DEBUG_README.html#sniffer Wietse
