Hi there. Basic info: - debian 7, 64bit - ISPConfig 188.8.131.52p3 Email problems - Do you use dovecot or courier as imap and pop3 server? Dovecot Problem description: Email are working normally, but the problem is when it comes to email forwarding. Example: - firstname.lastname@example.org is set in ISPConfig as mailbox and "Send copy to" is set to info@gmail_domain.com (I've tried to set it only as forward, but same result) - email is delivered localy to email@example.com and successfully sent to gmail according to mail logs, but I instantly receive message from Gmail with subject "Delivery Status Notification (Failure)" because of Shortly, as far as I understood, email is sent from server which is of course not in mydomain.eu TXT record and thus email fails. This happens with every single client that sends email to our mailbox, so there is no way to "whilelist" all of them. Solution would probably be to send email as original sender/original mail server/IP and not to send from this server. Postfix configuration: # postconf -n If anything else is required, please let me know.