[exim] how to avoid this error ?

Hello,
My exim server hang an I see a lot of messages in the log an on the
eximon screen.
errors :

2005-12-20 17:16:14 Connection from 62.23.9.83 refused: too many connections from that IP address
2005-12-20 17:16:14 Connection from 62.23.9.83 refused: too many connections from that IP address
2005-12-20 17:16:14 Connection from 62.23.9.83 refused: too many connections from that IP address
2005-12-20 17:16:14 Connection from 62.23.9.83 refused: too many connections from that IP address
2005-12-20 17:16:14 Connection from 62.23.9.83 refused: too many connections from that IP address
2005-12-20 17:16:14 Connection from 62.23.9.83 refused: too many connections from that IP address
2005-12-20 17:16:14 Connection from 62.23.9.83 refused: too many connections from that IP address

How can stop this attack ?

Thanks in advance
Guy