howto block postfix pop3 badlogins

hello,

i want to block badlogins for pop3 on postfix system.

i don´t know how to handle this, perhaps somebody could help..

my log entry´s look like this:

mail pop3[10305]: badlogin: mail.any.domain [10.10.10.10] plaintext username SASL(-13): authentication failure: checkpass failed

could somebody help out how to configure this in blockhost.cfg.

thanks..