Suitable port mail reject repeaters

[David Southwell]

Hi 

There have been numerous attempts on one server resulting in entries of the 
following type in the log:( [xxxx] is a domain for which we receive mail).)

Oct  3 07:05:39 dns1 postfix/smtpd[93611]: connect from 
mail.dolbeyco.com[70.61.148.178]
Oct  3 07:05:40 dns1 postfix/smtpd[93611]: NOQUEUE: reject: RCPT from 
mail.dolbeyco.com[70.61.148.178]: 450 4.1.1 <Novitsky@[xxxxx]>: Recipient 
address rejected: User unknown in virtual alias table; from=<> 
to=<Novitsky@[xxxxx].com> proto=ESMTP helo=<FRODO.DOLBEY.priv>
Oct  3 07:05:40 dns1 postfix/smtpd[93611]: disconnect from 
mail.dolbeyco.com[70.61.148.178] 

Where clearly the remote server is hoping to find we are either open to 
relaying messages or probing to find email addresses we will accept.

users with names that do not exist in the virtual alias table are being 
rejected. However the same group of servers seem to keep on repeated failed 
attempts.


What I would like to do is after receiving a number of attempts from a such a 
remote server to automatically refuse connections and reduce the log load. I 
believe there is a tool for doing that (say after a remote server has a 
speciofied number of failed attempts). I am sure there is a port that does 
this but cannot find it!!