Hello all! I have server behind FQDN GW. Server has not routeble ip (10.10.10.10) and my trouble is that domains who check my host name (or username?) reject my messages. Code:SMTP error from remote mail server after RCPT TO: <firstname.lastname@example.org>: host domain.net: 451 Sender verification faild for my_user@my_domain.net Any ideas?