Heinrich, The message you attached have no Return-Path:, which is curious (look at this message's source to see what I mean), but nonetheless, they're not quite what we need to look at.
What I'd like to see is the entire "bounce message that went to the list" scenario you're postulating, meaning that you'll have to find such a bounce message so we can look at the headers. Sandy Please visit http://www.ipswitch.com/support/mailing-lists.html to be removed from this list. An Archive of this list is available at: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/
