Messaging Gateway

Hi Experts

hope all are doing well

I have setup Messaging gateway 10.0.1 as intial implementation

with following details

DMZ-- i will put it later

1Eth0- with local ip

default spam filtering rules

content policy for media n exe files

as of now Outbound is working fine ,as for inbound i haven't performed the Natting port 25

i want to know it there any any ports required except 25 .

please advice this architecture is fine ,or do i have to add one more Eth card with inbound or public ip

thank you