When somebody tries to send mail from isconfig1.webdomain.com to mail.zimbraserver.com they get this error message... Recipient not accepted. Verify your relay rules My web pages and dns are in the ispconfig1 server and mail server is on the zimbra server. This presents a problem that I have not been able to solve. Should I just manually # mydomain on /etc/postfix/local-host-names Or can I somehow configure ISPConfig to allow sending mail to external mail server on a domain that it thinks is on the local server. Sam PS. I did configure the ISPConfig to know that this domain uses external mail server.