The very same problem started to manifest on a basically brand new MacBook Pro M3 on Sonoma and stil persists on Sequoia. It drives me nuts as I'm not able to efficiently work with e-mail. None of the solutions found so far worked for longer than a day or two. This seriously undermines my confidence in MacOS. I use Onedrive and Eset Endpoint Security (company policy), but I doubt all of the people reporting this do as well.