Positive pay service option is not available in my AX environment. It is mention in the tech-net site that you can set outbound port for Positive pay from System administration > Setup > Services and Application Integration Framework > Positive pay service > Outbound ports for positive pay.
But it is not listed in my environment. From where i can get this option.
It is there in AX 2012 R2 CU7. You need to check the version of your AX, it shouldn't be lower than AX 2012 R2 CU6.