Is there any way to configure delay in sending mails thru Postfix server (ubuntu 10.04Lts), what I'm trying to limit sending mail to 60 mails/min or 1 mail in 1Sec.
Policyd mentioned by mangia is better complete solution to throttle all dispatches.
In postfix however you can throttle delivery per destination with: http://www.postfix.org/postconf.5.html#default_destination_rate_delay
What goal are you trying to achieve ?
Global rate limiting is almost never the right solution.