How to increase the rate of mails from Interspire Email Marketer to Postfix MTA
 

Currently I'm getting a speed of 5 emails /sec from Interspire to postfix server. I tuned each and every parameter to the max level, even then didn't get any increase in speed.

I'm using a high end centos server with 24GB RAM, Xeon processor, 6 core
Please help me, I'm totally frustrated in this issue