16026 PostFix Help

Hello, I have a complex situation here. What I really need is some help. I have a very good programmer currently working on the sitatuation, but we are a bit stumped. I have a varpro autoresponder script installed on a domain that is hosted on our database server. We have a separate mailing server, postfix. I believe a script has been created to route mail from the varpro script to the mail server, I could be wrong. I can find out. The problem is this: Since we are using smtp, the outgoing mail is very slow, there's a bottleneck with the script, as the mail server we have is powerful enough to handle lots of emails. We have had mx records suggested to us a possible solutions, but since we are rotating IPs on the mail server every minute, my programmer says that won't work. We have a special setup, so normal methods of speeding things up won't work it seems. So, in the meantime, my customers are sending mail with their send broadcast features of their autoresponders, or uploading their leads, at which time their preloaded messages are sent to those leads, and it is very, very,very slow going. Hours and hours my page will hang on the sending page when I test the sending feature of my autoresponder account. Can anyone offer any help? It would be greatly appreciated. You will have to be willing to work with my programmer as well. Thankyou, Lisa