I think I've figured it out. The key is here: Jan 10 20:07:14 shelmerston postfix/smtpd[25950]: 7EC8D73CB9: reject: RCPT from sv12pub.verizon.net[206.46.252.148]: 550 <owner-saulnachem*XXX**VERIZON*[log in to unmask]>: User unknown in local recipient table; from=<[log in to unmask]> to=<owner-saulnachem*XXX**VERIZON*[log in to unmask]> proto=SMTP helo=<sv12pub.verizon.net> Looks like Verizon is using an anti-spam solution that actually tries to do an SMTP handshake with the sending server to check if the bounce address (aka the RFC821 MAIL FROM address aka the Return-Path: address) exists. So the problem really IS that Postfix on your server is not configured to accept probe messages. This means that once the Postfix configuration is fixed, the Verizon problem should be too. Postfix is outside my area of expertise, so I don't have the final solution for you yet, but I think we have found a very likely candidate. The question to be answered now is: How do you tell Postfix to forward all mail for HMSSURPRISE.ORG to LISTSERV and let LISTSERV decide how to deal with it? -- Francoise Becker <[log in to unmask]> Knowledge is just a click away: http://www.lsoft.com/optin.html