As @GiardiniDiMarzo says, the "fanmail" is really just junk mail and I absolutely agree it gets extremely annoying.
I wish there was a Reward Trait to block it or a feature on the mail box to stop it. There will be a reward in the household inventory of a mother plant souvenir but it's not really very decorative. I created an underground Strangerville room in the Science Lab where my Sim could store all of the Strangerville items, plants, etc. It's behind a secure door and everything is in pods, but it won't let me add the reward from her household inventory and I can't think what else to do with it.
So the reward I guess I really got from saving Strangerville is just a really nice area to build/live in that's safe from deathly plants. Well, the canyon area is anyway. I wish the main town was a little more upgraded after the victory in the same way Eco Living works.
