I have the same problem on a Mandriva 2007.0, the /var/log/mail/warnings shows those messages. There is nothing else in the log, but these messeges for every smtp connection is established:
Sep 15 14:31:43 bahn postfix/master[20118]: warning: process /usr/lib/postfix/smtpd pid 20301 exit status 1
Sep 15 14:31:43 bahn postfix/master[20118]: warning: /usr/lib/postfix/smtpd: bad command startup -- throttling
Sep 15 14:34:33 bahn postfix/master[20581]: warning: process /usr/lib/postfix/smtpd pid 20588 exit status 1
Sep 15 14:34:33 bahn postfix/master[20581]: warning: /usr/lib/postfix/smtpd: bad command startup -- throttling
SMTP connection then dies instantly with no other messages.
Sending/Receiving mail between local users is OK. Sending mail to external mail adresses (ex.
abcde@gmail.com) is OK.
Receiving mail from any external sourse is impossible, becouse stmp connection dies.