Post some details of your exact problems you're seeing and the steps you've taken to diagnose the problem..
Agreed and point taken. However, I have managed to track down what causes this and how it can be perceived to be an error.
OS - RHEL5
ZimVer - 5.02
Qmail-LDAP - 20060201
"netstring format error while receiving QMQP packet header" is a result of incorrect qmqp headers passed to postfix qmqpd service on port 628.
I managed to get this problem by telnet'ing to port 628 on the Zimbra postfix server. I did this because of some networking problems I was having.
It is not really a problem, just a case of not realising that I myself caused the error. The main cause of my problem however was that my two machines - the qmail-ldap and the zimbra server are both on 2 separate vlans and I never added both networks to the authorized qmqpd clients in main.cf.