timeout for POP3 query.

Is there a way to timeout POP3 query if they come to often?

More precise I want to know if there is a setting in dovecot that makes it ignore pop3 requests from a certain user if they come more often then a certain amount of time. I am looking for a setting in dovecot, not a firewall solution. I would like dovecot to answer something like "requests come to often, please come back later."

regards christian