Hi, my isp blocked smtp port 25 in attempt to fight email spam. You can see on my MT nat attached.
They give us a choice to use port 2525. My question is how do I change the smtp service port 25 to
2525 on my RB1000 MT. I've already tried to copy line 38 & 40 and change the Dst. port to 2525 but
still appear in red.

What chain does that rule jump to?

Does the jump target exist?

Maybe I'm not understanding the question, but... wouldn't it be easier to make a simple rule redirecting all port 25 traffic to 2525?

It's partially built into the Hotspot system. It install the following dynamic rule that is invalid (red in Winbox) since it doesn't point anywhere:

14 I chain=hs-auth action=jump jump-target=hs-smtp protocol=tcp dst-port=25

If you set an smpt-server in a Hotspot profile that gives you the following: The rule is no longer invalid since the jump target now exists. You can do that manually and also forward the port, but make sure to set the smtp-server on the Hotspot back to 0.0.0.0 since the dynamic rule created by having a value attached creates an entry you don't want:
No need to be more specific since the jump rule already does filtering by protocol.