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.
What goal are you trying to achieve ?
Global rate limiting is almost never the right solution.
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