How to limit connection

[Budi Febrianto]

Hello Linux experts,

      This actually a question from a friend, but because I can't
      answer it so I pass it to this group.
      He have old redhat 9 server with sendmail installed with pop3 server.
      Users can sent / receive emails to his mail server.
      
      The problem is, users set the automatic sent/receive in mail
      client too often... some set only 5 minutes. (every 5 minutes
      will check for new emails).
      
      He want to limit that, so user can connect to his mail server
      after specific amount of time, at least in here 15 minutes.
      So, if users sent/receive email at 2:00 PM, they can connect
      again to the server at 2:15 PM... before that will be rejected
      from the server.
      I belive this is iptables problem, not sendmail or pop3 server,
      but I have no clue.


-- 
Best regards,
 Budi Febrianto (mailto:bfebrian at gmx.net)