1 WAN and 2 GW in WAN

[SniZ]

Hi!
I have 2 ISP, in my router i have 1 WAN if and 1 LAN if.
In WAN if i plug switch with 2 modems in bridge mode from ISPs.
And each ISP have own GW.

How can i do nat 1:1 with my situation?
i wanna make give to my mail server internet, which give me my second ISP

[cmb]

With two Internet connections plus LAN you have to have 3 interfaces.

[GruensFroeschli]

Or you could let your modems run in NAT mode, and 1:1 NAT on both to the pfSense.
For outbound you could use the loadbalancer to the modems directly.

But this is a dirty hack.
cmbs solution is better.