On 24 May 2015, at 10:34, Christian Eichert <dovecot@zp1.net> wrote:

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."

http://dovecot.org/patches/2.0/pop3-throttle-plugin.c may be useful for you. Although that was written for Dovecot v2.0 and it probably requires some changes to compile.