How do I fix this error on Ubuntu 10.04 ?

Reading package lists... Done
Building dependency tree       
Reading state information... Done
postfix is already the newest version.
The following packages were automatically installed and are no longer required:
  libaprutil1-dbd-sqlite3 libcap2 apache2.2-bin libapr1 libaprutil1-ldap libaprutil1 php5-common
Use 'apt-get autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
1 not fully installed or removed.
After this operation, 0B of additional disk space will be used.
Setting up postfix (2.7.0-1) ...

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: numeric hostname: 202002
newaliases: fatal: file /etc/postfix/main.cf: parameter myhostname: bad parameter value: 202002
dpkg: error processing postfix (--configure):
 subprocess installed post-installation script returned error exit status 75
Processing triggers for libc-bin ...
ldconfig deferred processing now taking place
Errors were encountered while processing:
 postfix
E: Sub-process /usr/bin/dpkg returned an error code (1)

Even if I reboot, the same error shows up. Thanks for the help..