> The above 553 error was probably generated on your smarthost. > > Make sure your host is not called "localhost.localdomain" (in > /etc/sysconfig/network). Edit /etc/hosts and make sure your host name > is not in the 127.0.0.1 line (put it into separate line with your host's > IP address). thanks all - indeed the hostname was in 127.0.0.1 etc - fixed that and all is well.