Throwing a sticky on this because I have the same problem! I have it on my page not to send jumps unless I specifically ask for them on the forums and I still receive whole barns worth of jumps sent to my horses sometimes (which are pretty much only put in jumps when I'm sending to them and they're immediately removed). It's very frustrating!
Tl;Dr: please verify on bark paves, walls, and horse pages that your jumps are welcome. Thank you!
I think a good solution to this would be if they updated the horse description comment area to display text big enough for others to actually see! I'm sure if people could see the notes there not to jump that they would refrain. Could also use it for breeding notes such as "please retire all crossbreed foals not made pure" or "no babies in jump barns please!" Literally a million uses we could have if only the text were big enough people noticed it!
And PS, if anyone needs horses to jump, the ones I have in public are fair game! I also have a public jump barn, Dixie N Kasch Jumps XP (and LC) with TONS of crappy horses anyone can jump for free wins. 😁
What would be cool is if barns with the same IP addresses could challenge their other barns with the same IP address to horses that are not put in jumpoffs.
That way it can be just you challenging your own horses. :)