How can I create a distribution SMTP server?
I'm not quite sure how to word the title as I'm not sure whether this form of system exists but I'll do my best to describe what I'm after...

Basically we have a mailing system that only supports distribution to 1x SMTP server, however I would like to increase this to at least 4x SMTP servers. The mailing system cannot be modified (it's a windows based of the shelf product) hence what I would like is for the 1x SMTP server to not actually ever attempt to send the mail but instead to randomly distribute it among 4x separate SMTP servers.

I'm entirely happy for the 4x SMTP servers to be postfix on unix/linux and I'm happy configuring those, I'd just like some guidance on how I could configure the SMTP random distributor.

Thanks!
How can I create a distribution SMTP server?
===

I'm not quite sure how to word the title as I'm not sure whether this form of system exists but I'll do my best to describe what I'm after...

Basically we have a mailing system that only supports distribution to 1x SMTP server, however I would like to increase this to at least 4x SMTP servers. The mailing system cannot be modified (it's a windows based of the shelf product) hence what I would like is for the 1x SMTP server to not actually ever attempt to send the mail but instead to randomly distribute it among 4x separate SMTP servers.

I'm entirely happy for the 4x SMTP servers to be postfix on unix/linux and I'm happy configuring those, I'd just like some guidance on how I could configure the SMTP random distributor.

Thanks!