Dovecot Hacking attempt from Netherland

This morning I got another notification emails from my Firewall. Another Hacking Attempt to the dovecot, but this time, they are using proxy.

If you come from the search engine looking for this IP, please add it to your blocked lists

Time:     Sun May  1 09:14:55 2011 +0700
IP:       109.235.50.204 (NL/Netherlands/-)
Failures: 5 (smtpauth)
Interval: 300 seconds
Blocked:  Permanent Block

Log entries:

2011-05-01 09:14:53 dovecot_login authenticator failed for (windows) [109.235.50.204]: 535 Incorrect authentication data (set_id=account)
2011-05-01 09:14:53 dovecot_login authenticator failed for (windows) [109.235.50.204]: 535 Incorrect authentication data (set_id=account)
2011-05-01 09:14:53 dovecot_login authenticator failed for (windows) [109.235.50.204]: 535 Incorrect authentication data (set_id=account)
2011-05-01 09:14:54 dovecot_login authenticator failed for (windows) [109.235.50.204]: 535 Incorrect authentication data (set_id=account)
2011-05-01 09:14:54 dovecot_login authenticator failed for (windows) [109.235.50.204]: 535 Incorrect authentication data (set_id=account)