Can anybody resolve this:"temporary failure"?

bsd4lzx

My system is debian/woody ,postfix+Cyrus-sasl+imap,It works fine for about 2 months,but today I got these messages and many mails has been defered for about 5 days:
############ Copy from my /var/log/mail.log ############
Jun 25 00:46:56 mcgroups postfix/pipe[30702]: B5D2E24A3: to=<wuyu@mcgroups.com>;\
, relay=cyrus, delay=23963, status=deferred (temporary failure)
########################################################

I have already searched all over the google,this forum,linuxforum,bsdforums and many other mail/postfix forums but can not get any help.
Is this so sample that I can not get any help or so difficult...?

thanks!
bsd4lzx