SOLVED: How do I create a source NAT for a specific internal server?

[gctwnl]

I am migrating from EdgeOS (EdgeMax) to OPNsense. I don't understand the OPNsense UI/documentation on Source NAT.

In EdgeOS I have a simple rule that says:

• for inside source LAN address 192.168.x.x
• for destination port 25
• translate on WAN to IP one of my 5 fixed IP addresses

I have to recreate this on OPNsense, e.g. because the internal MTA must be outside DNS-correct when it connects to an MTA somewhere on the internet. When I edit an outbound NAT rule, I want to enter 192.168.x.x in some way in Source address, but I can't.

How do I create an outgoing NAT rule for a specific internal server (and destination port) and source-NAT it to a specific WAN IP address?

[gctwnl]

Answering myself: scroll up. The OPNsense GUI does something unexpected, when it opens up a drop-down, it opens it up somewhere in the middle. This I have have not encountered earlier, I was expecting it to open at the top and I only scrolled down.