Announce list custom success message

I’ve got an announcement list set up on a wordpress blog (
It’s running successfully, putting people on and taking them off. I’ve got custom pages for the subscribe, unsub, noton… etc etc. They’re all working fine.

However, when a person clicks the confirmation link in the email, they get a standard (ugly) SUCCESS screen.

I want to use my own custom welcome message.
I’m using this line of code:

Any idea what’s going on and how to fix it?