NAT 1:1 with an exception

[boujid]

Hi
we have 2 servers in our LAN that must be NATed 1:1 each one with his own external address
however this 2 servers must access an external server with a third external address
the configuration we are seeking is :
NAT 1:1
server 1 (192.168.1.1) (internal) <–> 192.168.10.1 (external)
server 2 (192.168.1.2) (internal) <--> 192.168.10.2 (external)

server 1 & server 2 --> 192.168.5.5 port 25 ===> 192.168.10.3 (external) --> 192.168.5.5 port 25

i configured the NAT 1:1 for both servers, then i added an outbound NAT toward the external server to use the third external address
but it doesnt work, it seems that the NAT 1:1 have the priority

is it possible ?

Thanks