When I send the mail via Outlook it bounces fine. It's only when I do it via Neomail's web interface that the bounced mail comes back to my catch-all. I think the problem is with Exim not trusting Neomail to change the outgoing mail header. This is talked about in Neomail's docs here: http://neomail.sourceforge.net/INSTALL However, looking at my /etc/exim.conf file I don't see anything that says: trusted_users = mail Also, what user does Neomail run under? The docs are telling me to add it to the trusted user directive of Exim so that Exim will allow Neomail to change the header.