We have a number of out of office email replies stuck in a loop between an x400 and local delivery queue. The original email is being delivered with a valid email address from our email host to our exchange servers, but in the header of the email the 'From' address is invalid, ie the . or underscore is being removed from the body of the email address leaving blanks in the address therefore when the out of office reply is sent, the system only sees the part of the email address before the space and thinks its an internal address turning the address into xxxxx@local (x's being the first part of the original email address) and because this is not a valid local email address the out of office reply gets caught in a loop betweent the queues with no expiry date or NDR notification. This only happens to a very small number of incoming emails and only happens with out of office replies. Microsoft have recommonded that we stop the McAfee Groupshield (ver 7.0.716) service on our Exchange servers, however I would like to know if it is possible to track the original email to see at which point and why the valid email address in the Return-path field in the header becomes an invalid address in the From: field.