Mail deferred by amavisd

[Andrew Ho]

Hi,

I checked the log, and amavisd send out this message.
Aug  7 13:33:43 mail postfix/smtp[27108]: 9EB99700176: 
to=<a...@dcf.com>, relay=127.0.0.1[127.0.0.1]:10024, conn_use=9, 
delay=17503, delays=17414/76/0/13, dsn=4.5.0, status=deferred (host 
127.0.0.1[127.0.0.1] said: 451 4.5.0 Error in processing, id=27311-09-9, 
quar+notif FAILED: mail_dispatch: no recognized protocol name: 0 at 
/usr/sbin/amavisd line 8516. (in reply to end of DATA command)

i check the deferred mail, and I found the following error in 9EB99700176.
    "%HTTP Error 500: Internal Server Error"

Any suggestion.

Thanks,