[CentOS] internal messages problem with postfix

Hello,

After a server crash, I re-installed postfix, cyrus-imapd, amavisd-new, 
spamassassin on a Centos 5.1 box. But, now mail system behaves somewhat 
different.

There is no problem with mail receiving/sending from/to internet.

Before the crash, mail system used to sent internal messages to 
root at example.com. But now, I can't receive internal messages as it tries 
to send them to root at server.example.com. I used the same postfix, 
cyrus-imapd, amavisd-new, /etc/aliases conf files from the previous setup.

Must be a configuration issue I overlook. Could anybody please tell me 
what to check?

Best wishes,
Mufit

main.cf:
mydomain = example.com
myhostname = server.example.com
mydestination = example.com ...

amavisd.conf
$mydomain = 'example.com';
$myhostname = 'server.example.com';