Hi, I saw a bounce message today (edited to protect the innocent): <user@domain>: 172.31.255.254 failed after I sent the message. Remote host said: 554 Filtered out by Filter 0 because "Received" = "from unknown (HELO ?192.168.0.1?) (192.168.0.1)" The client, for whome I was to relay, provided HELO approximately as: HELO [192.168.0.1] Which was indeed filtered to be "HELO ?192.168.0.1?" by qmail into the Received header. I was not able to find the document listing what contraints (if any) are placed on the string following a "with" such as HELO in the Received header line, however the RFC822 definition of <atom> does allow for '[' and ']'. I wish to find a tactful argument, rather than simply pointing out the lunacy of the destination's UCE filtering techniques. Curtis Coleman NOTE: The most fundamental particles in this message [EMAIL PROTECTED] are held together by a 'gluing' force about which little is currently known and whose adhesive power CC263 can therefore not be permanently guaranteed.