I use Tutanota as my primary email. There were problems with email delivery to the other email services like outlook.com, gmail.com... Now the situation is much better. Not perfect as it should be, but is far better. I see that Tutanota team really strives to block spam from their servers. I follow what's going on with this spam problem, and for me is not a problem to leave information about progress. I hope we will soon hit the send score 100