Last modified: 2011-03-13 18:05:58 UTC
In the "There is a new ticket" mails from OTRS there is no adress in the Return-path: header. (Perhaps this is the cause for Exim filtering failing).
According to RFC822, the Return-path header is set by the final transport, which is your MTA, not ours. See http://www.freesoft.org/CIE/RFC/822/28.htm