Rounting 2 ISP connections based on IP Protocol While using NAT

[nockerMan]

Im trying to modify our current configuration based on the following

We have to links to the internet a serial and ATM(adsl)
due to limitations placed by the adsl isp we need to send smtp traffic out over the serial line using a static ip (due to spam blocking on dynamic ip blocks)

here is a detailed break down. I have tried to use route-maps with some success but i down know how choose the nap traslation based on the ip protocol it i try with access-list that are port restricted it crashes the router(2611)

if inside traffic is smtp then use NAT with global address from serial0/0 routing traffic to serial0/0

if inside traffic is anything else route to dialer1(ADSL) using NAT from dynamic ip on dailer1

All inbound traffic comes in on serial0/0 so currently have default rount on this interface

Thanks in advance for any help