Ejaz: > How do I configure my postfix not to accept the emails which sent on invalid > address?,
It doesn't, unless you make a configuration error that causes Postfix to actually accept mail for non-existent recipients. http://www.postfix.org/DEBUG_README.html#mail > since morning we have been noticed that there huge spam > dictionary attack on our server, all originated emails are from random IPs > and random from address to the invalid recipient. See http://www.postfix.org/STRESS_README.html if this is slowing down your mail delivery, or just wait until it is over. Wietse