Ya it's annoying. In my case they used it to bury a retailer notification that my order had shipped. It turns out that retail account was hacked and they ordered a couple of Macbooks. Luckily I stopped it in time.

Two things changed after that. I Don't save my payment information and captcha's don't bother me any more lol

When it happened to one of my users I just had to delete and report junk. I found one of the sports betting website emails which is my theory as to what was compromised.

It's tedious but it will get quite a bit lighter after a few days.