Setting up postfix (2.9.1-5) ...

Postfix configuration was not changed.  If you need to make changes, edit
/etc/postfix/main.cf (and others) as needed.  To view Postfix configuration
values, see postconf(1).

After modifying main.cf, be sure to run '/etc/init.d/postfix reload'.

Running newaliases
newaliases: warning: valid_hostname: invalid character 40(decimal): ubunturocks.(null)
newaliases: fatal: file /etc/postfix/main.cf: parameter myhostname: bad parameter value: ubunturocks.(null)
dpkg: error processing postfix (--configure):
 subprocess installed post-installation script returned error exit status 75