Undelivered Mail Returned to Sender( centos mail server problem)

[beholdafrica]

hello everybody
i have a mail server which is running on centos after the installation it has work for some time now, but there is a problem now if you send a mail it will reply back with this message (Undelivered Mail Returned to Sender). i restarted the system and when it was loading i saw postfix fail. can somebody help to fix this please.

[redhead]

Look in the log file and error log to see if theres any indication why it fails.

With the info you've given here it's like saying - my car won't drive more than 80mph, and it's blue, please tell me why...