can you reach the SMTP server from the CentOS server? It seems that the emails arent getting out so that would mean SMTP settings could be wrong..
also make sure no firewall is blocking it. for example you can run iptables -F to flush the rules so you can test.
you will probably find the SMTP settings from this Japanese provider on their help pages..
e.g. I am with one.com and their settings are different :
but it could be something different in your case so you need to find that out first:
SMTP Server :mail.yourisp.net
SMTP Port :25